I tried a low power ultrasonic cleaner, and I was very disappointed. It cost about $125 and after several hours, the cases still had a lot of crud in the primer pockets.
I read the article on 6mmBR:
And they throw some light on the chemicals that make the process work, so when I have the loose change to get a larger ultrasonic cleaner, I'll give it a try again.
Fly... if you are allergic to the walnut stuff, have you tried corn cob? I use it in my large Dillon and the cases look like they just came off a jewelers wheel.