I went over the whole wheel with a red scuffing pad. I used sand paper and/or Dremel tool with sanding disc only on the really bad parts. You basically just want the wheel to be smooth all over, and etched so the paint will stick. I spent maybe an hour on all 4 wheels for the prep part of the job.
I used a primer to help promote adhesion. Some guys don't do this. I don't know if it's better either way. But it made me feel better about my work to prime the wheels first, then paint.
'92 YJ - heavily modded
'96 ZJ - heavily modded
'05 KJ CRD Limited - 370 lb./ft. from a 4-cylinder and trail ready. Pure awesomeness.
'11 Mango Tango JKU Sport - Mods
'12 Dozer JKU Sport S - 6-speed - ACE rock rails - Max Tow package - Daystar spacers - 33x12.50 Duratracs