(Ok, so it's a sponge? Big deal. Well, I've tried more than a few sponges, towels, and brushes for cleaning the ever-present brake dust from my 15" non sport wheels.

The sponges were either too big or too small. The one brush I tried just didn't cut it at all. Towels are just too sloppy.

This sponge (they make others of course) is shaped like a deep crescent moon, covers a lot of area but also squeezes nicely into the spaces between the spokes. The sponge cut my cleaning time (I use Maguiar's car wash soap & water) in half.

Also, you might try using a pair of rubber gloves, saves a lot of wear and tear on your hands....