How does he encourage the others to come out? So once he comes out they will be making moves to come out right behind him, within a full day?
OK, when they come out they try to climb on all the eggs and bounce around. While doing this they peep a lot except when they take a little nap in between the peeping. They usually will talk to the other eggs sort of, and the ones inside the eggs will get antsy and try to respond by peeping back but then they want out. So your peeper the one that's out actually will talk back in forth to those inside there shell basically saying. HELLO, WHERE ARE YOU GUYS, I"M A LITTLE LONELY OUT HERE. etc.. this will get the ones inside there shell still to speed things up a little bit.
Sometimes you can tell who's going to hatch next by watching the one who is already out. Usually they will lay next to or even put there heads on top of the shell for your next arrival.. Once he's out then they will go to the next one that's coming. I think its more like who ever's the loudest, will be the next one.