Completely sand the wheel to roughen the surface so the paint sticks better. Primer is a very good idea, use a couple of coats. Then spray 3-4 light coats of color. Dont cover the wheel completely with one coat, do it a little at a time with light, thin coats.
Definately use a clear coat. The prep will make or break the finish, and determine how long it lasts. I used Duplicolor wheel paint from Pep Boys. It matched the stock silver pretty well, but its not a perfect match.
