Navy, none of the "real" painters are answering so I'm tossing out that it makes a difference what paint you choose. If you're shooting single stage I've had some that mixes 1:1 with catalyst, some 2:1 and one that was 4:1 so the sprayable volume of a gallon goes from 1.25 to 2.0. Shooting inside and out, cab, fenders, hood & bed I'd say you'll need at least a gallon. Red pigment seems to be about the most pricey, but none of it's cheap any more.