You've got to be careful when doing this - but take some Simple Green or Eagle One All in One Wheel Cleaner and a green scrubbing pad.
Spray the wheel and pad with the SG or EO and start scrubbing. Most will come off fairly easily - however there will be areas that you will need to really scrub hard. Don't scrub in the same place for too long too hard.... If that doesn't work, I've tried some rubbing compound on the rims and that lifted some hard to get spots.
Then, definately, seal that bastid up with some wax....
The clearcoat on the rims will Thank you!
