Peter - I'd suggest that you purchase mixed stainless steel shot -
that is round, satellite, oval, ball cone, but avoiding the pins.
Pins can impinge on surfaces and in my opinion, cause more trouble
than they are worth.
As to fine silver bezels, you shouldn't have a problem, unless you
are tumbling many very heavy pieces of jewelry.
Further, when you run your tumbler with the shot - 45 minutes is
enough to burnish your work. If you run longer, you can develop
surface graining that shows as orange peel or roughness. Longer is
not better. Do run your work with an appropriate acidic liquid
lubricant, soap alone is not sufficient.
If you have access to US suppliers, you might want to get the small
book I wrote on the subject - "Tumble Finishing for Handmade
Jewelry". Gesswein, Otto Frei and Rio Grande all carry it. It deals
with all kinds of tumblers and media and has some cool tricks to use
these machines to save you a ton of handwork.