Wow! Canvasback, that is an incredible change!
Here is a similar result. I don’t have a before photo but can tell you I thought all the colors on this old Sauer were gone. What a remarkable change a sonic cleaning made! Afterwards I used Formby’s satin tung oil to protect it. Incidentally, the workmanship in these side locks is incredible. Gun is from about 1895.
Once again, I just tossed the whole action into the sonic cleaner without disassembly and when finished washed it thoroughly under hot water and dried with a heat gun turned low. Kept it hot enough to be very uncomfortable to hold. I know a better cleaning could have been done with a complete disassembly but I didn’t want to risk marring the screw heads. Lightly oiled all visible moving parts.