I have one of those electronic Game Doctors that spin discs to clean them, and I found that if you spray it like normal and then put your finger in the middle of the disc you can find the sweet spot where it spins and cleans the GC game as it revolves around your finger. Once it's made a complete cycle around I wipe it off with the microfiber cloth and buff it like normal. I was able to resurrect a very scratched Mario Party game like that and now it works like a charm.
Edit: I assumed you meant cleaning a GC disc if it was unreadable, other than that I don't know what else there is to clean on a disc lol.