Use a brush wheel on your flex shaft with tripoli. Then, clean it
thoroughly in the ultrasonic and use a soft brush wheel with rouge.
You can polish directly on diamonds, you will not hurt them. Sapphire
and ruby can take mild polishing before you’ll notice the facets
getting abraded. If the stones are already old and abraied you aren’t
going to hurt much. But once again, if they are genuine diamonds, you
can polish right on them and it will not affect them at all.
Hopefully I answered your question. If you are trying to polish
underneath the diamonds, that’s just a big pain in the behind!
Soaking it in pickle, running it through the ultrasonic and steam
cleaning are about your only options. I’ve been accused of steam
cleaning diamonds up a color grade or two! And ultrasonic out
inclusions to no avail.