I bought "zilla" brand walnut shell reptile bed media off amazon a few weeks back. IT was like $20 shipped to home and i have like 20lbs of the stuff, its about the size of a fertilizer bag!! Funny thing is like 90% of the review on amazon were for it as a tumble media!!
Now it works! Its finer than normal walnut shells but thats a good thing as it does not get stuck in your primer holes!!! It also is dusty. ( the Nu finish cuts the dust to nothing, see next comment) But if you put some of the "NU finish" car liquid polish for cars in there with it it will get as shiny as new brass. Now i see why amazon recomended it as a thing people often bought with the zilla. There is plenty of youtube vids saying to go to the pet shop to get your tumble media its way cheaper adn i think my brass is better looking than a guy who tumbled some i had and used real tumble walnut shells and some maybe polish.