I cleaned up the rims with this really cool brillo-like/type flapper wheel (p/n info in pic). The flaps have grit on one the sides of them. I was surprised at the results it has. Should be neat to use for other projects.

What really worked well and fast was putting the rim on a swivel shop chair and adjusted the height of the rims with blocks to meet that sanding wheel. I even added a block to the back of the grinding motor to get the angled surfaces.

The rims originally had polished center. But I wanted a cast look so I bought some Rustoleum textured Dark Pewter spray paint



Note block to tilt grinder and block under rim to get the rim up to the abrasive wheel.