I've done this, extensively. Produces beautiful, spotless, polished brass. Nothing else comes close. For the high quality of the result, there is no easier or more cost effective way. It's also fast, quiet and produces no lead/nickel/copper/etc. laden dust: quality of life things that make a real difference.

Things to know: Get magnetic stainless steel rod type media. It's not free, but lasts a long time. Use a good surfactant and soften the water, or use distilled water in the tumbler, and rinse with the same. Very important: thoroughly inspect for stuck media in the brass; it will stick inside due to water tension, and primer holes are eager to cling. The clean brass will oxidize because the process removes whatever protection the factory used and exposes unoxidized brass: figure out some coating that works for your use case.