I use WalMart paints for all of my rockets except scale models and metallic finishes.
First, go to the craft section and buy a 1/2" x 36" long dowel. Shove a spent motor on the end and you have your painting stick.
After filling the balsa with Elmer's Fill-N-Finish, I mount it on the painting stick, wipe the rocket down with a Walmart tack cloth, and give the rocket one coat with el cheapo Walmart flat white paint. After allowing the first coat to dry for a few hours, I lightly sand with 400 grit sandpaper to remove any 'fuzz'. Use the tack cloth again, and then I apply additional cheapy flat white as primer in 3-4 coats over two days . Do not spray heavy coats. If you are spraying lengthwise, and rotate the rocket 1/8 or 1/4 turn with each pass, the paint should be almost dry when you get around to the starting point. I then let the primer dry for a 2-3 days, so I t is good and dry. I then lightly sand the primer using 400 grit sandpaper. Now you are ready to paint the glosscoat.
Walmart paints are pretty good in this dept too, although the red is a bit dark. Wipe the rocket with the tack cloth, and spray a light coat of gloss color, just enough to cover. Wait 5 min and spray another light coat of the same color. Wait another 5 min and spray another light coat of the same color. Usually three to four color coats does it for me. Then let the rocket dry for at least 2-3 days before touching it.
You can mask and apply a 2nd color at this point, then let another 2-3 days for that to dry. Do not cheat on the masking tape. I use real, brand name 'tape for masking paint' usually 3m. It just works very well, and will not peel off your bottom color. I remove the masking tape as soon as I paint the second color, to prevent the tape from pulling off the undercoat. You can decal the rocket 2-3 days after applying the final top color coat. Then apply a finish of Future Floor wax.
The 'primer' flat white, the gloss coat, are usually 97 cents a can. You just cannot beat that!!
The trick here, and it has taken me many years to learn, is that you must not hurry. If you do, you end up frustrated by a saggy, fuzzy, or fingerprint laden paintjob.
Metallic paints asre a whole 'nuther ballgame, and it is best to tackle straigh glossy one color paint jobs at first.
Astronboy