This is off topic and I don't mean to steal the thread, but I have another great use for Cream of Tartar. It's the best thing going for cleaning the crud out of your stainless steel thermos. Put in a heaping teaspoon full of it, and a cup or so of hot water, and a handful of dry white beans (for an abrasive)....shake hell out of it for a few minutes, and it'll look like new inside!
Now - back to cleaning brass....if you don't have a tumbler, a wad of 0000 steel wool works well. I tumble too, but if you figure in the time it takes shaking the media out of the brass, wiping it clean, digging out the primer holes, etc., I doubt steel wool is all that much slower.