Okay, here's my experience with it:
I burnt some wood and threw water on it and gathered charcoal and repeated until I had a bunch. I had a heck of a time grinding it up small. I tried putting it between two plywood sheets and driving over it, and that didn't work for crap, and I don't even know what else I tried. Pounding it with a big metal thing in a drywall bucket. Nothing worked well, it was very very annoying getting it small and fine enough.