Level up to around lv55 and have one white mage (Rikku probs) and then have a Samurai to cast Fireworks (which hits all) then a Dark Knigth with Darkness. Constantly heal with 3xCuraga each turn (press the right directional button when selecting the target and all should be selected) then acst it to keep health up. Aim for one at a time to start, starting with Mindy or the smallest (can't remember which is which) hope i was helpful! ^_~