I buy those green Scotchbrite pads used for cleaning pots and pans. I shove one between the brake pad and the rim, then ride down the street and back for about a minute. Then swap it over to the other side.
Cleans up right up!
L8R
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"Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming, "WOW, What a Ride!" - unknown
"Your Bike Sucks" - Sky Yaeger