I use wonder wheels made by carplan(Tetrosyl),
Doesnt affect the paint finish in the wheels and it is fantastic.
You just paint the stuff on with a small paint brush which is supplied and leave for a few mins.
Then just rinse of with water.
It also puts like a film on the wheels so the next time you wash them its nowhere near as difficult although the BBS look a nightmare to clean.
Happy Scrubbing
Andy.