I don't have any direct experience with them. I did do some gunsmithing years ago. A lot of clean and repair.
I also fly RC planes. One of my friends picked up an Ultra-sonic cleaner at a swap meet. He seamed impressed with the results. I used to work in the Machine Shop, here. They used a small one to clean injector nozzles.
I think Harbor Frieght sells some smaller units. They also sell the cleaning solution. I think my friend used Dawn and water.
Tom