My best way for dealing with this fight was to get Wakka's Attack Reels Overdrive then have him and Rikku's Overdrive bars full when the fight starts.
Have Rikku mix for Trio of 9999 (I think you can use two Wings to Discovery to get it)
Then make sure you're at your best with the Attack Reels. If I recall correctly, getting "2 Hits" on every reel will have him attack 12 times. 12 * 9999 = 119,988.
Not quite the full 140k, but getting him down to 20k in just two player moves is a good start!