IME once you've started with anything abrasive on the transparent face you're on your own out on a limb. The disc may play afterwards or it may not. OTOH treatment with simple cleaners or "impedance matching" fluids like Finyl or Optrix can apparently make it easier for a player to read a scratched disc. I've also had some success making a copy of a damaged disc to CD-R. If it works, the CD-R plays (or plays through) when the disc doesn't.
