Shove a 3M Scotch Brite pad (the green scrubbing your pots and pans thigy) between the brake pad and the rim and ride up and down the block. That'll clean the rim braking surface and remove any "glaze".
Trust me on this!
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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