For future reference, I know a great glitch to level up Master (Final Mix exclusive as well haha)
In the second room of the Cavern of Remembrance, where Wisdom is required to proceed (or a high level Quick Run) Drive into master form and slash at the drive dispensers. You will gain many points and then walk to the room before it, and let the heartless kill you. You should continue in front of the door, points were kept, and drive dispenser is now refilled. Rinse and Repeat.
To fight the Org Data, you will probably need to wait a while. You have to make it all the way through Cavern of Remembrance (The Entrance is at the Postern and it appears when you see Sephiroth for the first time). You have to have Forms Maxed out to get to the second to last room.
The hardest part is definately the second to last room. You have a 1000 Nobody fight to finish before you can get into the Data Room and unlock the shortcut that you saw in the youtube vid.