[mapsjanhere]

Nothing wrong with a dremel and a brass wheel to get to hard to reach rust spots and to clean in the grooves of the slide. The biggest issue with going at it with sand paper is that you will lose the markings and soften the corners, both very undesirable. I would not use anything but 0000 or finer steel wool on a handgun to preserve the features.
But the real question is, how are you going to get the gun reblued? Whatever they tell you in the adds, cold blue will not give you back that factory shine, and hot blueing yourself is not for the novice. And if you have it redone professionally the gunsmith will have access to a bead blaster.