You pretty much covered it for ivory. Go slow, use sharp bits and belts, keep it cool (Do not dunk it in water).
Mammoth Ivory grinds, cuts, sands and drills very easy but stinks when you are cutting it. I have used it natural and stabilized. It is not really fossilized, it might be just at the beginning stages of fossilization.
Mammoth teeth still make me very nervous when working it. It is much harder and much more bittle than tusk ivory. I have only worked stabilized pieces but it cracks and chip very easy. Glue a piece of cardboard to the backside when cutting or drilling to help reduce chipping.
The main thing to remember is do not get either one hot. If it doesn't crack then, it will later. Even buffing on a buffing wheel can get it too hot. Work it a little, let it cool, and then work some more.