First off I\'d try to avoid having to file. But if you have to you can smooth the area better than the file leaves it with very fine abrasive paper/film - the finer the better. I have some 2,000 or finer and it\'ll leave GS pretty darned smooth.
You can repolish the surface of all putties, including GS, if you go to the ultra-fine grits, the kind of thing you\'ll find on a nail buffer - the ones I see are usually one side grey/white, the other pink. Whichever is the finer side (feels like there\'s no abrasive at all, just cloth) is something like 15,000 or 20,000 grit.
Anyone know, are there any very strong solvents that dissolve dried GS?
Einion