I dipped my toe in the water, so to speak, with a tiny little cleaner from Lidl, which did a good job of cleaning spectacles, watch straps, and jewellery, for which it was designed, but I soon found was not up to the job for even very small quantities of brass. It would only run for a few minutes, and took repeated goes to get a result, though it did get there eventually, until I think the transducer or electronics just wore out or overheated.
So that was a failure. But I'm still tempted to get a bigger one and give it another go.
I did get my best results using cheap diet cola with a drop of washing up liquid. It's dilute phosphoric acid, so I think similar principle to using e.g. citric, which is less readily obtainable. Tried the Sea Green, but found it ineffective.
Dull brass doesn't bother me, it may even have some advantages.
Since bought a Lyman turbo tumbler, but in retrospect I think I would have been better spending the money on a decent ultrasonic device. My cases are certainly shiney, but I doubt particularly clean inside, nor the primer pockets, nor the inside of the necks, if that really matters. The wet rotary process using SS media has it's attractions, but that's not an investment that I want to get into, nevermind the faffing about.
I think that just dunking into the US, 30 minutes later rinse in bicarb solution to neutralise, rinse again, put in airing cupboard in e.g. a bra net bag to dry overnight, might work for me. Using a low oven to dry is unlikely to be allowed by my girlfriend, and neither do I think that it's a good idea to share brass prep. with food prep.
The tumbler runs in the garage, but it is a dirty dusty process, all that stuff that does get removed ends up in the media, and it's not very nice for the health, once you look into it.
With US, it gets flushed down the drain, no worries about breathing it in, or the dust contaminating your workspace.