Cat litter is too dirty, it is basicly clay and will be way too dusty, great on picking up oil or tranmission fluid spills. Pet shop corn cobb is used for pet bedding and is too large and will not work that well. However, Zilla Lizard Litter is crushed walnut and works very well and can be found in your local pet shop. If you have a Granger near you, you can buy a 25 lb bucket of fine corn cobb for about $25.00 it is sold as blasting media. Cabela's and Midway USA also carry FINE corn cobb but runs around $18.00 for a 3 lb box.
I use 50% fine corn cobb and 50% Zilla with three cap fulls of Cabela's brass polish and that combo works extreemly well in getting my brass clean and shiny.
Good luck and stay safe.
Si vis pacem, para bellum