I use a mixture of fine alumina and fine plastic beads. I think that TP Tools calls it SPEED BEAD ABRASIVE: "80 grit Aluminum Oxide abrasive for fast cutting and 50-80 grit Glass Beads"
http://www.tptools.com/Speed-Bead-Abrasive,352.html?b=d*8019The industrial blasting firm that does big jobs for me has been willing to buy bags of those media for me (I mix them 50/50).
I try to clean all grime/grease off before placing parts into the cabinet.