Cecilia,
When it comes to icky, age hardened, goo and other solidified oils and greases I use Hoppe's #9 gun cleaning solvent. It's base is kerosene with a few extra solvents and it's not overly volatile like acetone, white gas or others.
Thanks for clearing up the use on the sand paper. I understand how that is as I've done it too on badly rusted pieces.
Joe