My first move was to get everyone Gained JP Up from Squire/Whatever. After that, I brought someone with the Knight’s skills to cut the enemy’s PA, MA, and speed, then just have the party pummel each other until I got tired of it. The Monk skill Chakra was really useful for restoring HP and MP, so you can keep it up for as long as you like.
Also, I don’t remember what chapter its unlocked, but Ramza’s Yell skill was pretty useful too, speed +1 for the rest of battle and it stacks.
The only thing to watch out for is gaining too much XP, since some of the random battles can get pretty hard without good equipment. If you’re careful, though, and enjoy a challenge, this isn’t much of a problem.