When you soak him, if you have a shoebox size rubbermaid tub with a lid, those will work well. Add about 1/2"-1" of lukewarm water, place snake inside, put lid on, and put the entire little tub into the snake's enclosure on the warm side. I'd leave him for a good hour since it looks like his entire head and eyecaps are retained. You can put a towel or something rough in the tub(wet towel ) as well as the water, so he can have something to rub on.

Did the previous owners say when the last time the snake ate? I'd get him settled into his new home first and leave him be for a week or so, and then try to feed him. This is alot of stress on the little guy/girl all at once, so working with him/her in baby steps will help minimize it.

I commend you on rescuing the poor little guy/girl from that place. We all know what would have happened to the snake if you hadn't.