When polishing a cylinder to improve extraction, it is not necessary to go into the front of the cylinder at all, just the part where the cartridge case goes. A big danger is getting carried away and polishing the front part too much so it is larger than the rear. When that happens, the case swells into the larger area and can't be extracted without a rod and a hammer.
But that being said, a few seconds with a drill, a split dowel and some 600 grit paper will sometimes work wonders. You don't need to go much finer than that, as you want some case wall adhesion even in a revolver.
Jim