What's the consensus magic potion for removing old, dried, hardened oil and grease from parts? I just came into a 1931 K22 Outdoorsman. It's in beautiful shape but needs a good cleaning. I thought I did that but looking closer there is varnish-like sludge in the camber recesses and a few other nooks and crannies. I'm doing ok carefully scraping it out with a dental pick and some magnification but something to soften it up a bit would make things easier. I tried some brake cleaner / degreaser but it did not have much effect. Maybe plain old Hoppes?