I haven't heard of this being used ....yet.
It's an abrasive and I don't know how abrasive it would be.
Rock tumbling begins with a course abrasive and ends with a fine polishing abrasive...but rocks are a lot harder than brass.

Try it with a fine grit and check often , stainless steel pins are all the rage now. Be sure to use it in a rubber lined unit like the Thumbler Tumbler , water may be needed like the stainless steel pins .

I still use polishing treated walnut shell media in a vibrating unit for mine , the water and drying makes a mess .

Gary