I have a rotary tumbler I use for polishing rocks and the like, and it
uses various grades of silicon carbide grit. This is probably too hard
and abrasive for anything softer than hard steel, though. However, the
final grit before the polish is a mild abrasive called a prepolish. It
is either tripoli or a synthetic abrasive that I'll have to look up. I
would try looking up rock tumbling media in google. I went looking and
found this site. They have both the rock tumbling media and the
specialized deburring media.
http://www.thumlerstumbler.com/accessories.html