Well what I normally do when crushing up yayo or pills, is I get this little miniature
flower sifter thing....I can't remember what its called, but its like a circular mesh thing that comes in varying sizes.
I use one of those and usually a pill case or something else hard and just rub/push/crush time the pieces of the pill or chunk of blow go through. I find this results in an ultra fine powder that it would take much longer or be impossible to achieve with normal methods.
You can do whole pills but its easier once their broken a bit. Oh and pills with beads will work but they require a little more force the good part about this in my experience is that it separates the powder from the little plastic bits, or most of them depending on size.