I bought some, hearing on here and other forums that it did a good job. After even 8 hours in my midway,(FA), tumbler, the cases were no better than before tumbling. Covered with fine dust and dull.
I separated them from it, went back to my tried and true corn cob, after just 3 hours, clean and SHINY I may try it again with some dyer ,(used), sheets and some FA polish just to give a fair trial. It's a bit more aggressive as an abrasive, so it should clean corroded brass better.
Harbor freight has it for blasting media. Cheaper even than petsmart.