paint?
Speed,
A difficult question to answer, consider, brand of paint? some brands, Dupont, claim 1 coat coverage ??.
Equipment used? Conventional spray guns or HVLP guns? HVLP's usually use less material as they don't atomize as fine and less paint goes out the exhaust fan.
Colors? dark colors cover better and usually require less paint to achieve desired results. Whites and yellows usually require additional coats.
Underlaying primer/sealers, a good idea is to use a sealer that is close to the top coat color, example, if you are painting a plane yellow or red, I would recommend paint the plane white first then top coating with the desired color.
Depending on technique and experience with a paint gun, you should be able to apply 1 coat using 2 to 3 quarts of sprayable/mixed paint.
Do the math, primer/sealer, 2 coats each, base color top coat 2 to 3 coats, trim, usually a quart will suffice. Clear coat ?, 2 to 3 coats.
Again, this is only an estimate, I am sure there are guys that will say they can doo it with less or more paint.
I have painted a lot of planes, hundreds, and this is only my estimate.
Dick