This article is from the Final-Fantasy and other Square Soft Games FAQ, by email@example.com (Nick Zitzmann) with numerous contributions by others.
Are the regular blitz commands too difficult for you to execute? Some of
them, such as Pummel and Mantra, simply involve executing a few steps on
the controller in sequence. Others, like Aura and Bum Rush, require
smearing your thumb all over the controller.
It doesn't have to be that difficult, though. For commands which require
smearing your thumb over the controller, you can execute them the same
way as the other special moves.
For moves which involve pressing the controller diagonally, you can
still pull them off by pressing the directional button once in the first
direction, then once in the second direction.
For instance: The Aura blitz is normally down, down-left, left, and A.
You can also execute it by pressing down, down, left, left, and A.
(If it still doesn't work for you, try pressing the buttons as fast as
you can press them.)
Some people will prefer this method of entering some of the more
difficult blitzes, others will prefer the "smear" method. It's up to you
to figure out which is best.