And the proper methods are...?
Not to disrespect you, JB, but I always find these threads a little funny to read because everyone has an opinion on what is best, but
nobody ever makes a declarative statement outlining the methods used by the professionals, i.e. PCGS and the like.
I challenge people who reply to these threads: Does anyone know the correct professional museum-quality restoration way to clean a coin without it losing any of its value? I've never found anything on the internet by anyone stating, "This is how PCGS does it" or, "This is how the Smithsonian would clean it."
The gauntlet was thrown a while ago. I dared someone to pick it up then. No one did.