As far as cleaning up ash, I have a thought that I haven't been able to explore because I'd need to create an ashy batch on purpose, which I never get around to. Maybe someone else could run with this and see if it's useful.
It's based on the fact that ash is very soluble in glycerin, more so than anything people usually use. I wonder what could be accomplished with glycerin (or a glycerin/water solution) and a paintbrush, especially for those of you who like the rustic tops and might sometimes get ash on them.
I find this to be an interesting subject, and thank you, earlene, for doing some testing.
TOMH, as an aside, I've often thought there should be something that will dissolve soda ash from soap bars. I say dissolve but am not sure if that is the correct terminology here, being the un-scientist that I am. But one thought I had was since (I think) ash is on the alkaline side, maybe something acidic would take it right off. Like a yin/yang thing. Well, I've tried citric acid solution (in water) and also vinegar (plain), but the results left me with a bit of a mess and the ash still sat on top, stubborn as ever. It's like some sort of mightily resistant superbug. But I'm still convinced there has to be something out there that will conquer it.