Oh, yeah:
I forgot to mention that you can also use industrial polishing media for cleaning brass------FAST! the stuff is made for west polishing (vibratory, tumbling, or agitating) and de-burring small machined parts. The media comes in cones, rods, triangles, etc. shapes.
You obtain it at jewelry supply shops or industrial tumbling and polishing supply stores. It comes in different geometrical shapes. The ones that I found work best for cartridge brass polishing are about 3/8" long x 1/8" diameter rods with tapered ends.
To use, you need a water-tight tumbler or vibrator media bowl, a squirt of dish washing detergent, and a couple pounds of the ceramic polishing pellets. Load up your brass, fill the tumbler with warm water, and seal it up and tumple away!