Before I start, I want to ask: which farming spot is better between Elite 4 and Kasen's house? I mean in terms of EXP gain x give time. Meaning: which is faster?
I've spent the last 2 hours on figuring out a strategy to farm the Elite4 Rematch, and I'm pretty close. I can farm them with only 3 (AChen, PAya, PShinki) except versus Shinki, where I managed to beat her once. Otherwise, I lose against Shinki (Dat Shinkis in the last sentence). I generally use items during the battle, starting from Yumeko: That's another thing that I wanted to avoid, since it's a waste of time.
Of course, my PAya has Salvo + Twister, and the 5-hits earth move (can't remember the name).
A note: when I started, both my Aya and Shinki weren't at lv 100, and still managed to help me. Also, I had some lv 80s (PMokou, DKeine, SFlandre) which I occasionally used.
Now, I would like some suggestion on where I can fix things. Here are my notes, copied from my handy-dandy notepad:
YUKI
Use AChen:
SMokou - Waves of Earth
SFuto - Godspeed Air Raid
SSuwako - Mist Fog
SUtsuho - Godspeed Air Raid
SYoumu - Waves of Earth
SFlandre - Chrome Ray
Heal, because Chen should have a damage caused by Mokou's ability
MAI
Use Chen (my Aya now is almost 100. I have to try to start with her here).
SElis - Waves of Earth
PNue (Camouflage as PRaiko) Waves of Earth, finish with Godspeed Air Raid
PKasen - Godspeed Air Raid, she will resist and probably one-shot Chen. If that happens...
Switch with Aya
PKasen - Twister
DYuuka - Transcend Form
SRemilia - Twister
PRaiko - Spirit Stone Jig
probably she can't take it. Switch with Shinki and finish things.
Heal
From here, is kinda random. My lv 80s (now 90s) help me out, and that's what I don't want. I want to beat all 4 with only 3 charas.
YUMEKO
Enemies weakness are (All CAPS mean a double weakness):
PSakuya - Fire Fighting Sound
PTenshi - Water Nature Fighting
SHijiri - Wind Illusion
PKokoro - DARK
PMiko - Water Earth Dark Illusion
SYumeko - Fire Earth Fighting
Heal
SHINKI
Enemies weakness are (All CAPS mean a double weakness):
PMima - DARK
DYukari - Steel Illusion Sound <-- Tons of both Focus and Spread defense
PToyohime - ELECTRIC Poison
PYorihime - Fire Dark
PSariel - Steel Fighting
PShinki - Steel Illusion SOUND