I have only recently got a second guinea pig and I find the best way to do it is to cuddle the older pig who is more used to it and then let him down for a run. Then I like to get my baby pig out and sit cuddling him for a bit while my oldest, Biscuit, has a run around. I would like to let my baby Nutmeg have a run around too but I'm very worried he'll run away and not follow Biscuit back!