I used to shoot machine guns in Idaho and had a real mass quantity brass processing need. This method I came up with works so well I have never bought any equipment to clean brass. When you do 1000 cases a week it has to be fast.
1) Deprime brass. I use a 45ACP FL die for most of this but have a spare blank die w/ decapping rod for the rest. A dedicated depriming die is the way to go.
2) Using a RCBS primer pocket brush chucked into a drill (or drill press if there is lots of brass) I clean the primer pocket.\
3) With a correct caliber bronze brush in a drill/press I clean the necks.
4) Hottest tap water you got with powder dish
washer detergent (1 -2 tbsp) in a recycled 1 1/2 gallon ice cream bucket. (Blue Bunny Cookie Dough is by far the best bucket made. Use only these!) Stir with a wooden spoon.
5) Pour into a colander and drain. Rinse in hot water. Pour them back into the the bucket and stir them in hot water again and drain.
This is the plastic colander I bought at a garage sale 20 years ago for $5. I paid too much. Get a plastic one @ Walmart.
6) Use 2 Tbsp of citric acid in just enough hot water to cover the cases. Just enough water and no more. I source my citric acid from a local Health Food / Organic Store called Marlene's. They order 5 lb containers for me for cheap. One container is almost a lifetime supply. Probably can find it on Amazon for cheap. Stir for two minutes and let set for five minutes then stir again and drain. Rinse and stir them in the bucket full of hot water for about two minutes and drain again in the colander.
7) If the cases are not bright enough for you do step #6 again. But stir for 5 minutes and let stand for 15 minutes and the stir for 5 minutes more. I have picked up years old range trash and it comes clean after this second acid bath.
8) This step is very important to neutralize the acid. Repeat step #4 with the powdered dish washer detergent as Cascade and similar detergents are a mild base. They will neutralize the citric acid.
9) Rinse at least twice in the hottest tap water your hot water heater puts out. Stir for at least 5 minutes each time then drain in the colander. Pour the cases onto an old towel and roll back and forth until they are dry.
10) Buy your own aluminum cookie sheet so your wife doesn't go ballistic and put a sheet of aluminum foil on the bottom and pour the cases on it and spread them out. Knock them onto their sides as the primer pockets won't dry out if the cases are standing up. In a 150 to 170 degree and no more oven let them set for 1/2 hour then shut the oven off. In an hour you have clean and dry cases.
This whole process takes about 15 minutes of effort and not more than 1/2 hour total before the cases go into the oven. With cooling time I have clean cases in less than 2 hours. I use Hornaday's One Shot spray case lube to size the cases for FL sizing and then clean them in dish washer detergent and double hot water rinse with an oven dry. The Hornaday lube is water soluble. Then it's time to prime and load.
This process is so easy I do it most of the time for all my loading.
As this picture shows the before and after on some truly grungy 556 range pickups you can see how effective it is and does not require any expensive equipment. The insides of the cases are as clean as the outside. There is no residual abrasives left in the cases to scratch your dies or rifle bore or plug the primer hole. You may be able to get cleaner cases with another method but it won't get you any more accurate ammo or be nearly as economical.
I started with Sulfuric acid and then tried Phosphoric acid but settled on Citric acid as it is friendlier to the fishes and other God's creatures and is easier to source. The citric acid is much more controlled in cleaning and does not appear to dezinc the brass.
I promise you that this is so simple and effective you will sell your tumbler / vibrator after trying it. If not you should have a bowl of Blue Bunny Cookie Dough Ice Cream and reconsider the wayward decisions you are making in your life.....
KB