I have the larger of the harbor freight models, and I have found that it really only has the power to clean about twenty .308 cases at a time. You can put a lot more in at once, but it just takes a lot longer to get them clean. Also, I put my cases in a container, which is filled with the cleaning solution, and the cleaner itself is filled with water.
I have found that this process works very well:
http://www.6mmbr.com/ultrasonic.html
Using these containers to hold the cases:
http://www.etundra.com/Camwear%C2%AE...fhu=3735333038