I have both ultra sonic ( does not work well enough for me, so I just do small batches of nickel cases in mine ) & I used to rotary tumble with cob media, but have made the switch to the stainless pins, & my cases look like new when I get done now
I have just hand washed, by putting some dish soap in a plastic sandwich box with .25% fill of brass, & letting it soak, & giving them a gentle shake every 10 minutes or so...
BTW... I do have a scratched 357 mag sizing die... best guess, is when I 1st started loading, I didn't want to tumble the nickel cases, as it polishes off the nickel, so I must have run one in with some grit, & scratched the die... so you do want to clean your cases, somehow, to avoid scratching your die... ( when your die gets scratched, they can scratch every case you run through them ) so it's worth cleaning the cases