Quote Originally Posted by <<MiKo BaHaMuT>>
Believe it or not hahah, I didn't get those special weapons ^^"
My easiest tip is...

1. Buy many al-Bhed potions for Rikku.
2. Make sure you've got all the aeons (including Magus sisters and Anima)
3. Charge up all the aeons overdrive gauge before battling Jetch.
4. REMEMBER to charge up YUNA's OVERDRIVE gauge

In battle
1. Use normal attacks to kill the first form
2. Keep an eye on your HP.
3. After your characters take much damage, switch to Rikku and use al-Bhed potions to heal. Remember to always heal
4. The party member I suggest you to put in front lines are the ones with most HP (ex. Auron, Wakka or Tidus)
5. Yuna must be in the front line in Jetch second form
6. Summon all the aeons and use their overdrives
(Note: They might be killed)
7. Finally after using them all, use Yuna's overdrive.
8. Summon the strongest aeon that survived (usually in my case are Anima or Magus or Bahamut)
9. Summon them and use their overdrive.

Note: putting Lulu in the front line is not a very good idea...
In my case, her HP is low and as well as defense ^^"

I know you'll be able to pwn Jetch with this strategy haha.
That's a great strategy.