I use P21S and Sonax, like everyone else on the forums. But I only use them once in a while; for maintenance washes a microfiber and soapy water gets the bulk off - especially if you seal the rims.
335xi sedan 6MT, Premium, Cold Weather, iDrive, CA, iPod
Black Sapphire Metallic, Black Leather, Aluminum Trim
European Delivery: April 28 - May 7, 2008
Performance Center Redelivery: July 11, 2008