Dry then grind.

If the OP is after a powder then it has to dry sometime, its easier to avoid making a huge mess if it dries as a whole hull and is then ground.

I have a wild black walnut tree on my property, and I know that in stores, they charge an arm and a leg for the product, so this is a good post b/c I'd like to make make my own as well.
Brendan, question, what is OP? How would you say to dry it, just set it out in the sun a few days? How do I know when its fully dried? What do you think is best method for grinding? Could I just use a mortar and pestle?

Herbalistic, would I be able to just chop them in a blender, and then dry them further to make a powder? I am not too keen on using tinctures myself, so I'd rather make a powder.

Thank you everybody for helping me out. ~Karen, Ky

Black walnut hulls are a pain in a** to process, but here goes: collect the walnuts & peel the green hull off with a SHARP knife. Cut as fine as possible. Dry to a leathery texture (they will be black), then grind in a coffee grinder. Dry again. Powder in a mortar & pestle if you want a super-fine powder.

Powder's nice for rinsing graying hair, but is typically used to dispel intestinal parasites.

Another, way to get rid of parasites which doesn't involve lots of peeling & drying of walnuts, is to eat a few cloves of raw garlic at once, which paralyzes the parasites, then wash them out a few hours later with a couple cups of apple cider (the real stuff). To make quick cider, pulp 2-3 apples in the food-processor, pour a cup of boiled water over pulp, cover immediately & let sit overnight in a cool place but not the refrigerator (too cold). Then drink.

Sorry-- strain the pulp, then drink the liquid...