I use a 1/2" dowel in my collet chuck. I turn it down a little, if I get it too small I wrap it with painters tape. Kind of sloppy, but at slow speed it will center itself enough to get it done. A little taper made with the painters tape at the bullet end will hold it in place.
I buff them on my buffer. I have a separate set of buffing wheels for brass. I use metal buffing compounds from Caswell Plating. DO NOT MIX them up with your buffing for finishes. Everything has a zip bag, put them away immediately after you are done.