Thought I'd post update regarding my case cleaning with ultra sonic cleaner. The one I bought holds 750ml. of water, so its only a small unit. I've used it for a couple of months now and very pleased with results. First ultra sonic cleaner only lasted for a couple of days before it failed but I'd bought it locally and returned for replacement and the second one has worked perfectly ok. The speed the cases are cleaned is very quick, only 10 minutes or so, and the pockets don't need cleaning seperately and there's no tapping each case to get the tumbling media out.
A friend bought an ultrasonic cleaner after seeing the results of mine and was initially disappointed, however he used it without the citric acid. When he used the acid his cases were very clean as well. So the acid obviously does something.
I've got a black powder revolver and put the cylinder, hammer etc. in the ultrasonic cleaner and they come out spotless. That was something I hadn't considered in the beginning, so overall very pleased. Within seconds of starting cleaning the liquid around the items being cleaned gets cloudy, I can see the dirt being lifted of. At the end of the cleaning cycle the liquid in the tank is so dirty I can't see through it.
I appreciate I don't fire a massive amount of ammunition so I can see the tumbler with pins could be the way to go if you do get through lots (or a larger ultra sonic cleaner) but for what I do at moment it does all I want it to.