Hi Badger, I've been blending and dying for many moons so please don't go the coffee grinder route until you have at least tried wet blending as I was instructed to do by Eric Leiser years ago. Add a little detergent to the water, blend,drain in a sieve and you'll end up with a neatly matted falt. Just remember to cut synthetic yarn into short pieces beforehand because the longer fibers of a synthetic will tangle (either wet (or dry).
I know you'll enjoy the process.