I bought a used S&W Model 65 that looked like the previous owner never cleaned. The entire face of the cylinder was black. I got it spotless with a Lead Away cloth and a bit of Flitz. The trick once that is done is to minimize the buildup. I keep a light coat of Corrosion X on the face of the cylinder, and when I get home from a shooting session about 85% of the carbon wipes right off with a little solvent. The, I stand the revolver up vertically, dab some Hoppes #9 on the remaining burn marks and let the gun sit overnight and let the solvent work. The next day almost all the remaining carbon wipes off, and any minute traces that don't will clean up with a little Flitz. I truly believe that the light coating of Corrosion X, or probably a similar product keeps the carbon from bonding in the first place, and also believe that if you give solvent time to work, the need for harsh scrubbing is minimized.