Actually this works wonders, but BE CAREFULL, use it to much and your disc will no longer work at all. To be on the safe side just use it once or twice. I did my Legend of Legia disc, then let a friend borrow it, and had to do it again <_<, after that it skipped around on my ps2, but was fine on the computer for a while...after a month or so it just became unreadable.I heard that Disc Doctor thing you can get at wal-mart works well. Basically it skims off a layer of the disc and shines it all up. Its worth a try
Best bet is to try the toothpaste trick, that works wonders and as long as your toothpaste doesn't have crystals in it, there is no harm, it worked fine on my Blood Omen disc that I bought preused and was HORRIBLE.