Dry tumbling choice of media

I don't do a lot of reloading so this isn't meant to scale to thousands of rounds a day/week/month/etc.  For cleaning brass, I've been using the same ultrasonic cleaner I use for cleaning gun parts and occasional carburetor and other small engine parts.  That's worked for me, but I don't have any really filthy or corroded brass either.  I mix about 2-3ml of dawn dish soap and a teaspoon of citric acid crystals in a 1 gallon ziplock bag and fill it with water and 50-100 spent cases.  Seal it up and put it in my ultrasonic cleaner that's filled with clean water.  I turn on the heat for the cleaner to 50C and then set the timer for 45 mins.

When that's done, I rinse the brass and put it on a cookie sheet and throw it in the oven at 200F for 20 mins or so.  

That's been working for me.  I re-use the liquid in the bag a few times before I dispose of it.  Easy peasy.

Best,

I use Corncob with the green additive, not sure what it's called.

I tried the walnut with rouge (tufnut?), what a mess that made, dyed my fingers, the brass seemed to get a red tinge too.