I think most people here use a belt sander of some sort, and then finish either with a buffer or by hand sanding. If you don't have any experience, I would recommend getting some files, and various grits of sandpaper. You can work almost any handle material you want with these, and it does not take as long as you would think. Rough shape the handle slabs with a course file, and then sand with rough sandpaper untill all the file marks are gone, then use progressively finer grits until you are happy with the finish.
If you are thinking about bone, it smells better if you work it by hand then if you use a grinder. It is also harder to screw up with hand tools.
Kyle Fuglesten