208 - What is Thrumming in jewelry making?

Thrumming is simply the use of long strips of abrasives, like sand paper, to smooth and polish in tight or hard to reach areas. I like to cut long strips using cloth backed fine grit papers, which are more flexible than paper backed and last longer.
Because the area that your sanding is usually very small, you can often start with pretty fine grits. My typical progression is 600 to 1200 to 3000 to 14,000.

This process also works using leather that has been imbued with diamond paste or polishing compound to get the final polish.

The polishing strips I show at the end are actually dental polishing strips.

They can be found here:
https://amzn.to/42XMNwQ