this may be a obvious method but.... have you tryed the good old swivel method?
basically shoogle your ps1 around in different directions hold it upside down etc, in all honesty i have not found any game i cant get to work with a little patience using this method. no buffing no paste no thing just plain old will power alone. (and i have had some pretty damn badly scratched games work doing this)
((oh yes i forgot to add this will most likely only work on the ps1, if its a ps2 im afraid this is meaningless))