Awwww, Tsuzuki, thats actually easy. You know you have reation commands at that point. Only this time, instead of just triangle its X as well. If you keep jamming on those two buttons the entire time rikku/sora will dodge/reflect almost all of the shots. You may still get hit a few times, but they will avoid most it. Also just a lil bit extra:: THE FIGHTS ALMOST OVER AT THAT POINT!!
Well try it and let me know how it works for you.
