Foaming tire cleaner from the automotive section -- Armor All works well, Son of a Gun does nearly as well -- the quality difference is about the same as the price difference. Spray on, walk away, come back with an old towel about 20-30 minutes later, and wipe it off. Does okay with the chain, too, in case you have to lube it later. If you have little ones, start this about 10 minutes after they fall asleep.