I've used a combination of some of the tactics already set. Always I remove all counter abilities that would deal damage to an enemy. Then I kill all but one enemy. Afterwards, I try to find a cross-like piece of land that's completely flat, and place all my characters on the sides of one with punch art in the middle. This character continually uses Chakra, usually the melee jobs are accumulating, and the mages cast buffs. haste is always good because you get in that many more turns than the enemy.

I usually do this until I have enough JP for all the abilities I want in that particular job for each character. After this, I repeat, and have the character master the next job in that battle, until I have them around where I want them ability-wise. Then I just power through for Gil to buy the best equipment I can, then progress the story.