Oh Davy, this is my favorite. We've done this once before on the forum, but let's add to it now.
Tip: Everyone uses a coffee bean grinder to blend dubbing. The problem is that the dubbing fibers tend to stick on the clear dome due to static, and fail to make contact with the spinning blade. When they stick to the dome, they don't mix evenly. Two solutions: make a cardboard disk that fits inside the chamber, just above the blade. The disk will trap the fibers. Second tip: spray the inside of the blender with anti-static spray like you use in the laundry. The spray is also good for any hair stackers you may use.