I would go ahead and soak it. The BP I rescued awhile back, had horrid retained shed on him. Though I wanted to give him some rest, I just had to soak him. Honestly, in an hourlong soak, all the skin came off. So yeah, I would def. soak!
I would definately quarantine for as long as you can stand it. At least 2 months, in my opinion. Are you planning on taking him to the vet? It might just be a good dieda to let him settle in before doing that, unless you can get him in right away, which is tough.
I am really glad you got the poor little guy. it burns me up to see how people neglect their BPs. I wish you luck with him.