Have you tried Psycho Penguin's faq, A l e x, or even better, Djibriel's, at Gamefaqs? Those are probably the most in-depth faqs I've seen, and should help. Other than that, I don't remember what exact towers to go through, etc.

http://www.gamefaqs.com/console/psx/game/562865.html

Edit: And this should be moved to the FFVI forum...but I'm sure a mod will get to that eventually.

Edit: And indeed they did.