“......throwing the brass in my rotary tumbler, some hot water.....”
Not for me to ask or wonder why, another shooter/reloader/etc.. found a a commercial/industrial blue print developing machine, serial #1 of 2, compete with wheels, stainless steel tube, chain drive and variable speed controlled drive motor. He wanted help in turning the machine into a tumbler, the machine is now a wet case rotary tumbler with a 7 gallon fluid capacity, and he has enough cases to fill it, again and again etc.. Then for some reason I do not understand he purchases this little bitty tumbler that uses stainless steel pins, back to “Not for me to ask or wonder why”. He could have added stainless steel pins and lime shine and water that does not stain?
I use ground up corm media and nothing, for the worst of cases I use vinegar for a maximum of 15 minutes for the life of the case. I could use vinegar for less time if I used a rotary tumbler, if everything was made of stainless steel, or plastic etc..
When using vinegar the cases must be rinsed and rinsed etc., again, I do not make it a habit of cleaning cases in an acid, I use vinegar to reduce tumbling time, some times from 4 days to 2 hours.
Using water in a dry type tumbler is a load for the motor, too much weight, I have ceramic media, same thing.