|A shoe polishing brush|
It is important to keep these brushes free of hardened cement, as a brush containing pieces of hardened cement will scratch the leads rather than darken them. As soon as the polishing is finished, inspect the brush for little balls of cement. Rubbing the brush against a clean rough surface will clean it while the cement is “wet”. Also running the brush at an angle on the sharp edge of your work bench will clear some of the cement adhering to the bristles.
|A polishing brush with slightly stiffer bristles|
If the cement hardens, you can clean the brush by crushing the hard balls of cement with a pair of pliers. Or you can just get a new shoe polishing brush.