I always seem to have cob media in bottom of my brass storage bins when I tumble with cob, no matter what I do to separate, how many times I have changed my system, it is always there.
I JUST made the switch to SS media 2 weeks ago, WOW, so much better overall. It does take a little more hands on time, but the results are much better, both the clean factor as well as the separating factor. The SS media is heavier and just seems to separate better. It can cost a little bit to get into, I didn't do it for a LONG time until I stumbled on a used Thumler for $60. $10 new gasket, $6 belt and $6 plastic knobs and it is running like a champ! I have put probably 4k worth of pistol rounds thru it in just over a week and half. There is a Co on FB that sells a granular SS media, I tried it and found it is a pita to work with as it is so small and light that it tends to flow with water. It also sticks to hands, tumbler etc and can be tough to keep where you want it. I am borrowing a 5# batch large(.062"x.500") SS pin media from buddy below, finding it is much easier to work with, drops clear of brass well and does not stick to everything. I think sort of a std size is more of .047"*.500" Runtime can vary depending on tumbler used. My Thumler is an old one for rock polishing, so runs at 1/2 speed, thus I run it 2x as long, that works well though as I just set it up to run overnight, empty and reload in morning and run a batch while I am at work. Then repeat in the evening and run overnight.
A Friend of mine from over on Waguns.org put this video together, covers SS tumbling pretty well. I follow the same routine and find it takes about 10-15min for me to do the process of switching a batch over to the dehydrator and then starting the next batch in the tumbler.