I wouldn't quarantine from a rescue either. Agree with all that has been said about giving the cage/hutch a real good disinfecting and cleaning and move around houses/toys etc. If you already have one pig in the hutch then it sort of becomes 'his' hutch, 'his' territory, and by disinfectanting (is that a word?) etc. it neutralises the area in terms of smell, so both pigs hopefully start off equal, so it's not disinfectanting with the idea of killing off any germs, but to get rid of territory. Definintely agree with Lou and Al, feeding time is ideal as they are more interested in food.
(If I visit this rescue centre for you to pick up your piggy, Biscandmatt, I hope I don't get tempted myself...it will all be your fault! lol)
xx