This is by far the most arduous and time consuming task in this process, and there isn't a lot a guidance I can provide you. I don't think there is a single dominant method for smoothing the ring, just start out removing your largest bits of material, and end with your fine sanding.



For example, this was my process:

1. Grinding away the burrs with the dremel

2. Hitting the ring with the roughest belt I had

3. Dropping the grit until I was satisfied with the shape

4. Using the fine wheel in the dremel to smooth the ring to a satiny kind of finish



Bone tends to crack and brown under high heat, so try not to let it get hot, keep a cup of water to dip it in between sandings.