I saw a while back there was a thread here where someone had cleverly laid polymer clay in grooves of a stainless steel piece.
I decided to have a crack at doing the same, and also bought myself a rotary tool with diamond burrs to polish it all up.
I first roughly polished the external parts of the ring (leaving the inside intact for character). I then smooshed the polymer clay into the grooves on the ring, making it all as neat and flush as possible. In the oven at 200ºF for 20 minutes or so then let it cool. Once cool I finished up the grinding and polishing.
Here are the results using black polymer, and also a granite looking polymer with grit mixed in. I like them a lot