Do you just want to remove tarnish or is the old wax and gunk that needs to be removed? Usually no need to use grit unless you need an abrasive action.
When cleaning up our brass dops (good condition, just a bit of tarnish from being exposed to the air in the racks while waiting to be sold), then we tumble them in stainless steel shot - works really well.
cheers
Leah
cheers
Leah