Do not clear coat like you would anything else, do not use primer.
here's my recipe:
have done it a bunch. It defininatly works best on publics. The steps for best results are:
1. sand it with a fine grit paper.
2. Clean it really well, make sure that you dont leave any cleaning soaps on it.
3. spray in a bunch of thin coats, and the best spraypaint to use is Krylon flat white. do like 5 to 10 thin coats... so each coat goes on and almost instantly dries. The idea is that you don't want it to set up into a thick layer, so you HAVE to spray it on thin, so the new coats don't solve the old coats and create one really thick later.
4. for custom graphics, sharpies work the best. just keep it moving, because otherwise the sharpie ink will act like a solvent and absorb paint up into the sharpie, ruining it.
5. Use a thin coat of clear coat. not very much is needed, jsut make sure it is covered.
read that thread, read my posts.
Flat White Krylon is the only paint I reccomend. It bends much better than any other paint I have ever used. Other paints crack and chip off.
that's how i did the ones in the video above, give it a try.