the rims in my avatar and in my members ride i painted myself...
1) i cleaned them laquer thinner
2)sanded with 320 grit (do not sand hard or go higher than 600 grit, you dont want to create a buffed sheen, you just need to allow for the paint to adhere to the old surface)
3)mask the wheels/tires off appropriately
4)i used duplicolor durable wheel paint, its 3.50 a can, buy 1 per wheel, and when you paint start with a light dusting, take your time, thinking about how you overlap your spray pattern
5)i suggest allowing a week or 2 for hte paint to setup before mounting tires or expecting them not to chip...even the best paint will chip if its not given enough time to setup...
6)enjoy!!