Tell him not to worry about something which he cannot control.
This. Also, even if he gets an exploding offer, the judge might allow him to finish his interviews before making a decision regardless, since he has the interviews lined up already and isn't trying to leverage into a "better" offer or anything. Or he/she might not and the friend will just need to decide on the spot then. It's out of his control at this point.
My judge has extended exploding offers to people he really likes, but he also doesn't really do things according to the hiring plan, so it's not typically the case that the kid has multiple interviews going on or anything.