We made a small sketch first. Then the sketch was redrawn more accurately on graph paper. Then we enlarged it onto canvas on which we had drawn an enlarged grid. We made an enlarged outline and then painted it close to the colours on the sketch.

Use waterbased colour paint i.e. EMULSION paint mixed with water, i.e. the type you would use to paint walls, that's much cheaper than acrylic. Don't use the paint for doors (i.e. lacquer/enamel paint) as that's too glossy. Oil paint is too expensive and takes to long to dry. We mostly used camel EMULSION paint.

Have the foundation colours and then just mix any kind of colour you want. As for some parts we didn't need a lot of a particular colour, we used some acrylic paint to mix them.

What kind of backdrop do you have in mind? For what play is it?

Muslin or calico [unbleached} is a much cheaper alternative to that of canvas. In most cases you are able to get this from 60" to 109" wide, off the shelf. [Large upholstery Companies purchase this in bales based on it?s weight & it comes in various lengths, packed straight from the manufacturers machine, rather than in rolls because it?s cheaper - you might be able to do a deal with a friendly local upholster?]
Place your panels horizontally & either stitch or glue the salvage edges together with an epoxy 2 part contact adhesive. Horizontal panels work better because the stitching or gluing will restrict the natural stretch of the fabric & cause wrinkles which are difficult to hide. Horizontal  seams can be usually incorporated as part of the horizon or lines of a building. Vertical seams are difficult to mask the puckering & wrinkles that will always be visible no matter what you do - because of the downward weight & of the hanging material.
At the Tail of the drop, fold and make a Tail batten [pipe] pocket with a folded skirt, this allows the batten to be suspended evenly & tort while only the skirt touches the stage.
At the Head glue or stitch Jute webbing, which you can get in a roll from an upholstery supplier, Fit grommets [kits are available from Camping, DIY or hardware stores] evenly a bout  12" apart, starting from the centre of the cloth  & working outwards to the ends, so the cloth will hang properly & tight. Cut rope or cordage into about 2? length ties, to suit the width of the head batten & allow for a lakshead & bow knot to be tied. {Choose a different colour tie for the centre grommet. This will help when loading  the cloth & centring it on to the head batten [barrel]}. Fold the tie in half to form an even loop, put the looped end thru the grommet & then stick the 2 tails thru the loop & tighten into a larkshead knot. [ ensure you set the ties up all the same way & start the knot from the same side each time, I always start on the downstage side, then the knot tightens the cloth all the same way & I find the cloth looks better from the front.] Use a normal double bow knot to tie it to the head batten [the same as you would use to tie shoe laces] you will find it this is the  best knot to use, when unloading the cloth from the head batten, as you only have to  pull one tail to quickly undo it when striking or folding it for storage. [use an indelible marker pen on the jute header to describe the cloth, with it?s scene title, this makes it easier to quickly identify it without having to roll it out to  find what drop it is?]
You can also add a grommet & tie to each corner of the cloth to help with tenoning it, especial along  the tail batten when using sand bags or stage weights to tighten the cloth & hold it down. Cloth stretchers come in handy & are easily made from 2 pieces of plywood with a bolt & wing nut off centre to tighten down & vice grip the cloth edge, a hole drilled in the off stage side of the boards, to accommodate a rope, which is knotted at the hole to form spacer or some other spacer added in the sandwiched boards, will give gripability to the holding edges of the boards, when tied off stage to an anchor point.

I always find it helps to mix size, fire retardant & whitener in one application to apply it, by spilling some on to an area & spreading it out by using a broom or mop to cover it quickly before hanging, as a base to bond & proof the cloth prior to painting. However your local fire department may require the retardant to be applied in some other way? - check with them first, on the method preferred & the best local supplier.
Try & paint your finished cloth while it is hanging in place, this will help with perspective while painting & sight lines from the auditorium. However this is not always possible so you have to rely on your minds eye to view it from a distance. Also this cuts down on accidentally walking on the cloth & the paint adhering to the floor when dry!
Even if you use the graph method or just your talent, think out a plan of action to create the scene by  the line of the horizon/sky & foreground then the middle. After you have finished the cloth & painted it with plastic, emulsion or poster paint.you may still have wrinkles after it has been flown. Use a mist sprayer of water to lightly dampen on the back of the cloth of the effected wrinkled area,  this only takes a short while for the cloth to naturally stretch the material & the wrinkle should disappear. Don?t saturate the cloth, as this may cause colour bleeding of the paint on the finished product.
 However you may get cloth rolling at the edges & this can normally be rectified by painting the back of the rolled area to help flatten it out. Also if you cut the cloth slightly narrower at the Tail this will avoid wrinkles as well.  [calico & muslin will tear straight with the weave across the width, if you start by cutting a small nick in the salvage edge]

By the way with most paint it cheaper to get white bulk paint & add colour tints to mix up your required colours.

I hope this helps you with your new experience ?DM?.

Eagle and Gaafa... Thanks so very very much for all your wonderful suggestions.  The snap-line idea is a great one and especially good to remember to keep the inch mm thing consistant.

The detailed description of the work you guys did is very helpful.  I am a person who likes to have as much information as possible before I start a project.  I am fairly skilled and creative, but having lots of perspectives on a new task allows for a much less mistake and more good creativity. 

I especially love book recomendations.. Books are my passion

I am also a fiber artist and will always try to use fabric in everything I do.  It is interesting how we find different mediums which are more comfortable than others. 

My husband is great with wood and fairly drools when a truckload of planks goes by.  As for me I could crochet a house if I had the right fiber and a big enough hook  :)

20? seems rather high?
Do you have a Proscenium or a studio space to work with?
Also if your raiding hubby?s tool kit for a ?Chalk line? -  This is also useful for marking out the sage stage area, for sets & fly line drop locations.
While your on the raid - grab a spirit level, plumb bob & hole punch (used for Canvas or Leather work, to make it easier to apply the ?grommets in the head of the drop). Also if you are using the graph method, a ?blackboard? ?Compass? or ?odd leg Protractor?? will come in very handy as well in marking out the grid lines & grommet locations - centre to centres! Further what might make it easier is to use a projector as well as the graph. Add the graph lines to the image on the slide or acetate (Mylar) overlay, if the scene is a complicated structure.
Chookas ?DM?

An ?Odd leg protractor? is simular to a blackboard compass, except that the marking leg is bent.  So when you extend to the required size, the marking leg implement is at the same angle, as the holding point of the pivot leg. This does make it marginally more accurate & even wear on the maker, rather than then wearing in down on one side & the mark becoming progressively bigger. But it is not something you would possibly have to worry about for the normal theatre ?gaf? methods we use, unless you wish to be very accurate!
The venue sounds like a ?Concert Hall? style venue, used for the more discerning  ?Toffee Nosed? Muso?s??
Don?t worry you will win the War in the end.  It will change when the newness is worn off & the ?blue rinse set? eventually evaporate! Given time the Management. will realise the on going cost of maintaining the floor & resort to covering it with ?Masonite? hardboard sheets (I think this is what you call ?Luan??) & eventually painting it, as a more cost effective method. I only hope they don?t opt for a ?stage cloth? covering of Burlap or the like, which will make it more difficult for you!
With the dimensions of the backdrop you gave, I assumed it was a Studio or Lecture space, because it was higher & more squarer, than is used in most theatre & amdram spaces.

Chookas 'DM"