Stainless steel shot in a tumbler works very well for me, there
is nothing that I know that will polish chain so fast and so
efficiently in about a half hour. Any gemstone in a ring or
broach that is harder than 6.5 is left on and is never a problem.
I use 8# of stainless steel shot in my tumbler (Lortone). The
shot was originally made up of spheres with a ridge around the
circumference, what looks like 1/8" wire cut at an angle on both
ends and pieces of wire sharpened at both ends 1.5 x 12 mm (About
1/16 x 1/2 inch). On flat silver surfaces I found that these
sharpened wires left very tiny pits on the surface, though for
chains they would be fine. The first two shapes described have no
doubt been tumbled and burnished because all their edges are
smooth but the finer needles are something else.
It was simply a matter of taking out those needles and setting
them aside. No further problems. As for rust, yes under certain
extreme conditions stainless will leave a trace of rust so after
use I drain and rinse the shot then spread the lot on a large
bath towel and leave then for about a hour. I then pour them into
an empty coffee can and keep the lid on and that eliminates the
rust problem. The SS shot is used with about a level teaspoon of
powdered soap in the tumbler.