Because of the low cost and lack of V.O.C.s, I have been experimenting with latex house paints for scale models. This is what I have found.
The primer should be a primer/sealer with lots of body. If you want to add details such as panel lines etc., add corn starch at a ratio of 2 paint to 1 c.s. to give the primer even more body. Spray on two or three coats with about a 1.7mm tip, letting the primer dry for about an hour or so between coats and about 8 hours to finish. Before pulling off the tape or mask, give the edge a quick wipe with 220 grit sandpaper and the edge will be nice and sharp.
Spray on the color coats as desired using exterior grade semigloss paint and a 0.8 tipped spray gun. I prefer to purchase the bottles of tint from the paint store and mix my own colors, but the store will match any color you need if you need large quantities. When spraying over a mask (tape, frisket etc.), apply a light coat of paint and dry it immediately with a hair dryer or heat gun, then apply additional coats. The bonus with using latex is that you don't have to apply lighter colors first. The paint has enough body that light pigments will cover over the darker ones.
Finally, coat the entire model with the desired gloss of polyurethane laquer. Three thin coats should do. Remember to apply your decals after the first coat of clear. I'm currently experimenting with waterbourne laquers - we'll see what happens.
Oh yeah - I prefer to use a gravity feed spray gun, available almost anywhere.
For those of you tired of the high cost and smell of oil based or epoxy paints, try latex and I guarantee you'll never go back!