You can take a junk 6X9" car speaker (Or any large speaker) and make a home brew "sonic" cleaner. Just get yourself a stainless steel tray that you can put the biggest of your guns, make a plastic/wood/metal spacer to make up the space between the top of the center of the speaker and the bottom of the tray, and put it together with a ton of silicone. Let it sit for a couple days to dry. The spacer is needed to quiet it down. Without it, it works fine, but is very loud.
Hook it to a boombox or any other amp and play some bassy music, put your gun and some solvent in the tray, and wait a few minutes, and it does a nice job. Every nook and cranny is cleaned, except for lead from the barrel, of course.
I made the last one I had for nothing out of pocket. It lasted 10 years before the speaker fell apart. I'm going to make 2 more with the OEM junk speakers out of my truck. They aren't worth a damn for music, that's for sure.