Even if there is surface damage to the pad, there is plenty of foam left on the pad which you can still use, you just need to work at it a little bit. You can buy a Duo Spur and it comes with 2 abrasive plates (like a cheese grater) which will slowly remove the top layer of foam, leaving you with a fresh pad again after a few minutes. The downside to this is that it won't work on a PC or UDM and probably not with the Flex either, only a rotary polisher...