Yeah. I agree with greasy fingers. If it's circulated and found in rolls I don't use any extra care really. As far as cleaning goes some water aND a q-tip goes a long way, for harder gunk even a toothpick.
I don't use the same tactics on bought coins though or coins with good value but the usually good to xf $5 or less coin found in rolls, yeah I'm not going crazy about it. The amount of rub and wear a coins gotten in regular business use.. I don't think cleaning up some gunk with water is going to make a difference even if I do some rubbing with my fingers, or a q-tip ect. Just don't go as far as polishing.
Now, chemicals.. I don't see much harm in acetone on silver. I'm uncomfortable with using it on copper though. Not sure how that works out. Copper in general can discolor so I just stick to water usually.