I know there are several people who have painted their rims, but since there is no walkthrough that I could find, I figured I'd post this up. I decided to paint my stock rims (now my winter rims) bronze after reading through this thread:
Here are the supplies I used to get it done:
-Duplicolor Bronze Wheel Spray Paint - x3 cans
-Duplicolor Wheel Spray Clearcoat - x2 cans
-Sandpaper - 320 grit - 2 sheets at least
-Paint thinner or varsol
-Rags or paper towel
-Old deck of playing cards
Step 1: Clean the wheels
Mine were especially dirty, so this was a long and tedious process... I used hot soapy water and some old rags to get the majority of grime. The tar spots were the most annoying and I found that scratching them off with a fingernail was better than trying to scrub them off, which just smeared them worse.
Step 2: Sand everything
using 320 grit sandpaper, I went over everything to make sure that the new paint would have a good surface to bond to.
Step 3: Wash
It is crucial to make sure you get all the dust and dirt off.
Step 4: Wash Again
This time wipe down the entire rim with the varsol or paint thinner. The purpose of this is to get any oils or grease off of the surface which would keep the paint from bonding properly.
Step 5: mask off tires
at first I used some plastic to mask off a majority of the tire, then used an old deck of playing cards to stick between the rim and tire. This proved to be the easiest way to get even the part closest to the tire painted. Mask off the tire valve.
Step 6: Paint and more paint
I would recommend a very well lit area to work in, especially if the color you are painting is dark. For the fronts of the rims it is easy to see the coverage, but the backs are very hard to tell what is covered. I did 2 coats on the backs and 3 coats on the fronts. wait 10 minutes between coats.
Make absolute sure that you done put it on too thick, or else you will get runs, and if you wipe them off, everything will come off, even if you're on the 3rd coat and the other coats felt dry.
Step 7: Clearcoat
Wait an hour or two after the last coat of paint before putting on the clearcoat. Avoid waiting too long or clearcoat could cause paint to wrinkle. I did 3 coats, but you could do more to extend the life of the paint.
Step 8: Let it cure
I left mine a good 24 hours till I put them back on. The paint cans didn't have a recommended time period to wait, so I just guessed