I have a friend who owns a professional coffee grinder that makes some of the finest ground coffee I've ever seen. This work very well for filling cracks, but it has me thinking. I'd like to be able to grind filler (coffee, wood, soft stone, etc) much smaller even than this stuff... I'm talking the consistency of fine enriched flour. Not in large amounts... just a little at a time.
Anyone have any ideas? I was thinking maybe a mortar and pestle?