Final Fantasy X HD Remaster -- Jumbo Flan Battle

I always use Tidus, Rikku and Wakka, unless otherwise specified. All battles use the characters' Celestial Weapon fully powered. The armor equipped is: Break HP Limit | Auto-Haste | Auto-Protect | Ribbon. I don't require anything special for this battle, because Jumbo Flan never gets an actual turn in to attack. I tried a secondary method with Anima, but that battle took ~20 seconds longer than this one, so I used this one instead.
Battle explanation: 1st turn use Reflect on any character. 2nd turn use Slow on character who has Reflect. You can't use Slow directly to Jumbo Flan to slow them down, which is why you do this at the start of battle. 3rd turn Doublecast Ultima -- doubles the amount of damage done per turn, and requires you to use less turns in battle. 4th turn and beyond use Copycat -- deals the same amount of damage per turn, and uses up 28MP instead of 180MP per turn.