I simply wet sanded my wheels with 600 grit sand paper, washed them thoroughly with soap and water, let them dry over night, masked the tires and valve stems, wiped them down with acetone, and hit them with a spray bomb. After an overnight dry time, I then used a clear satin finish to provide some protection from brake dust. They've held up quite well for almost 2 years now, and I get compliments at nearly every show.
If you want more than that, simply take them to a body shop and they can professionally spray them in the booth. Ask for a clear coat -- it'll really help with brake dust which will stain the paint over time.