You would have to inquire with the Swiss powder people on fineness of their powders. The "crushdown powder" I make with a small mortar and pestle is finer than ffffg. I use Goex. McMaster Carr has bronze screens you can put in an embroidery hoop to sift with, once you find out grain size data. But practically for this discussion a dust black powder under a cap in a foil new made cap shell will work with dust powder, and avoid stacking those toy caps to get the ignition power needed. Before I got my M & P I used am empty round shoe polish can and a 1" wooden dowel piece to crush powder, Gently. A little tedious, but workable.
BvT