Ginger,
Frankly, coin-cleaning is among the least of my skills - at very least, it's one I have only begun practicing recently, as opposed to decades doing ID's, etc.
Now, for a generally clutzy person like myself who's never been given high marks for fine dexterity - or for that matter, physical grace of any sort - some of the best results I've had beyond that which can be expected from DW soaks and denture-brush scrubs were achieved with the aid of a stereo "dissecting" (ie: great depth of field) microscope at 5x or 10x. Anything more powerful is unnecessarily close and you are likely to "get lost" in terms of your orientation to or where you are on the landscape of the whole coin. A fine-pointed pin, usually held in a pin-vise, is generally the sort of tool you want to use. Under this level of magnification, the point of the pin resembles a bulldozer blade and a very fine layer of encrusted dirt seems like packed sand a meter deep. If there are voids between crust and coin which can be exploited for flicking pieces of crust off whole, they show-up as caverns or cliff-dwelllings under the 'scope.
Of course, it takes forever to do it this way - but that's the point. If you don't have the coordination and dexterity of a brain surgeon, you probably want to do whatever is necessary to make the micro scale on which you need to operate to distinguish the often vague boundary between crud and patina seem as "macro" as is practical.
Mark
