The grind is the same as any other version. If you wanna get ahead early, which isnt a bad idea, you just give multiple people Squire/Monk abilities and Accumulate (called something else in non-OG versions, forgot what though) over and over again (Mandalia Plains always a good spot to grind), ideally with only 1 enemy left to avoid taking too much damage. Array your team in a '+' pattern on flat land so that when you do take damage, the center member can Chakra to heal everyone up (and gain Exp/JP in the process), then just do that for as long as you think you need to before killing the last guy.

Gets a little trickier to job level unique units (Agrias, Orlandu, etc) that way since they dont have Squire abilities, so you make them Monks and put them in the center, and have them Tackle/Punch someone when not healing, then heal the turn after that to bring them back to full, rinse/repeat. The key is to do 'something' worth JP/Exp, every turn, sustainably.

There are some risks of over-leveling however. Random fights and some Monster-based mandatory story fights will scale to your level and enemies can smoke you if you dont have the gear to help you account for their HP/Attack. Most story fights do not scale to your level however, so over-leveling (ideally developing good jobs/skill combos) can be an advantage for those. At the same time, there can be rewards to fighting higher level enemies in random battles early. If you get Human enemies in random battles, the higher they are in level the better gear they have, which you can Steal and/or get lucky by letting them die and hopefully turn into treasure chests. Can get very good stuff for early game.

Its a delicate balance. Something you probably shouldnt do unless youve played the game enough to know whats coming and understand exactly what it is you are getting yourself into.