On a skill level of 0-10 what do you rate your ability to clean coins?
I just think that messing with them at all is inviting trouble unless you are the kind of careful and methodical person that can spend hours on one coin.
It might be easier to strip off everything and re-tone it. I don't know, let us hear what others think. I mean _I_ would _not_ do so, but I know I don't have the skill. I would leave it alone.