All of them that I've done have had decent brushes without too much wear remaining. I simply disassembled the starter, cleaned everything with CRC electronic circuit cleaning spray, clean up the copper contacts on the rotor where the brushes rub with fine sand paper, spray some dielectric grease on the brushes and make sure they move freely against the springs, put some silicone grease in the bearing ends and reassemble. Pay attention to the location of any washers that come out. They usually work great after a good cleaning and lubing.