Kroil is very good and wicks thru quickly. A days soak in kroil and a light brushing with a tooth brush then wipe with soft flannel cloth should be all it needs. The frozen parts can be lossened in the soaking and either soft jawed pliers. ( I have both leather and lead jaws made up) or it its a thread with no smooth wrea then jam nuts and a wrench working slowly and carefully. I made some soft jaw pliers from 4" channel locks for the bench. One set has thick leather jaw pads epoxied to the pliers jaws. Another set has lead jaws poured into them. I put steel plates on each side of jaws with a small parallel clamp holding them with a filler in front and back then poured soft lead in. About 1/8" thick