I actually use a combination of both. My brass tends to come out super clean and smooth doing it this way as well. I use walnut first. For the super dirty brass, i do a quick buffing with a dremel before dropping it in the walnut, or i toss it. Once thats tumbled for a few hours, i throw it in to a corn cob media that i use to sweep away the walnut for about 10 minutes(i hear that walnut can scratch your dies). Then i use another batch of corn and leave it in with a capful of nufinish for a few more hours to get it super shiny.