When you get it home, they are easy to get working again. On the bench remove the rear cover after marking its position. Use wood type sand paper to clean the armeture. Crocus cloth seems like the thing to use, but it can get stuck in between the segments and cause a short. Wood type sand paper will not short. Clean the brushes with a clean cloth, and make sure the springs work freely. Install the brushes so far that the spring holds them by thier sides, then spring them loose after the end cap is back on. Of course you will clean everything while apart and put a dab of fresh grease in the end bushing.