Avoid Traps:
Whenever you need to get through a room filled with traps, hold R and press Y to bring up the quick equip menu. If done at the right timing, you won't get hurt.

Dressing Room Access:
When starting the game, have at least 10,000 Meseta in a character's coffers (not in the bank). Note that any changes you make in the dressing room will cost 10,000 Meseta when you're done.

Thanks to Revolution readers Amon and Erebus!