Just wanted to share this since googling it didn't give me a good answer...
There is a point is the Black Omen just after you encounter the two Nus who will either sell you stuff or warp you back to the entrance.
You fight a yellow beast, whatever he is, that you can charm speed tabs from (and do so forever, FYI...).
The next room contains two of those blue Gato robots. If you status protect yourself, which you should be able to with Amulet and... some helmets or something... Chaos won't affect you. You can now fast forward the fight ad nauseum... up down, up down... and level 99 everyone pretty damn quick. Thanks to that fast forward! Just spam the a button. I got everyone to 99 in less than an hour watching Seinfeld.
The trick is, they'll halve your HP, but if they can't cause chaos they can't ever actually kill you. And there was a save point just a room before for shelter use. So there you have it.
Tech points, if you need them, can be from those big eye things that always lock your techs/items. It's some outrageous number I forget, also pretty wasy.