I didn't see this Drive gauge trick mentioned so I'll mention it now. Alternatively to transporting off a world, go to an area where your party departs. Normally when they depart from your party, you can talk to them as they walk around the area. Everytime you re-enter an area like this, your Form reverts back to normal and your Drive gauge is back at max. It's similar to teleporting off a world but takes a little less loading time. I normally use it in the room right before the final battle to level up some of my forms.