I use walnut to clean dirty brass, as the walnut is harder and does a much better job of removing carbon. Add a cut-up dryer sheet to help keep the media clean, and discard after every load.
Use corncob to polish and do a finer clean. It's much more absorbant than walnut since it's more porus and softer. Adding a capful or so of Nufinish car polish will do a fantastic job of polishing brass or loaded ammo. Again add a cut-up dryer sheet to remove excess polish and lube. Discard after every load. Add a capful of mineral spirits when the polish seems to quit working. That will soften it and rejuvenate the polish.
And use the finer 20/40 grade of cob and you'll never have to worry about punching media out of flash holes. I've been using this combination for about 20 years and haven't found anything cheaper or better.