ORIGINAL: SwampCollie
A scotch-brite or 3M coarse scrubbing pad. The backside of a regular kitchen sponge will work in a pinch.
Agreed. And make sure to condition in one direction and condition that same direction every time! Put the scotch pad down on the slate at the 9 o'clock position and move to the 3 o'clock position. Then, lift the scotch pad up off of the slate and the put it back down on the 9 o'clock position and repeat. This gives your call consistancy.