Just for the sake of clearing things up....
To beat the game riddiculusly fast (im not giving a specific time, there are alway's differences in the odds/Exp you get per battle.)
If you concentrate on using cloud and alway's giving him the better weapon, withought leaving the main story, you fly through the first disk in litlle time....(((DISK 1 is the longest disk in my experience)))
Shorter for the second disk (lots of luck to you)
When Ultima weapon flyes out, take an hour or less if your luck is good, and kill him (gets clouds best weapon) and cloud should be a fairly high level just for following the main story, after ultima is dead, grab Slash-all in the forsest and use that. (Do not master it, wasting time, flash no good for bosses anyway.)
When you get to the battles in the end, Eg: bizzaro sephiroth, slash all attacks all the pieces, you should do around 6k dmg or more at this point in the game, and he dies withought ever neading to switch parties etc....
Then summons are also effective, yet they waste time (physical attakcs are best, then have one char always cure if needed), even if you never get bahamut zero (a whole 2 minutes to get him if you followed the main story to a "T" and not miss the huge materia.) I
f you want to spend an extra few minutes, with slash-all, ribbon, and a cold absorbing armor... you can easily get omnislash in half an hour
dont forget, put long range on cloud, and stick him in back row,
this means skip getting vincent and yuffy, speed through the text, dont ever visit fort condor (before huge materia makes you) dont stray from the main story, hell you can avoid most of the treasure chests in the game to! many are wasted footsteps
(why take a minute walking for a potion or pheonix? they do add up....)