If you click on Cloud's icon, he gives a hint:

Quote Originally Posted by Cloud Strife
It's at the top of the volcano.
There's only one volcano dungeon, an optional place. Go there and have a character use Move-Find at the top. Rafa is a natural choice because her Bravery is so low.

As for Limit, it's like the Archer's Charge, but with a meelee weapon instead of a bow and arrow (although Charge works with meelee weapons as well). So equipping Short Charge will make your life easier.

I'd put my money on Finishing Touch, since it does a nice amount of damage in addition to some nifty status ailments.