For me it was the other way around. I always used a belt and felt like my body was relying on it too much. Ive deadlifted 495 with no belt and just chalk and my core felt the best it ever had.
use it whenever i go above 3 plates on squat or DL. no point in fuckin up my back for a lil extra core work. but those are usually the last 1 or 2 sets.
LOL, No rrehab, i actually hate pain meds. But it was so bad i had to start taking them. Lasted about a month, then i thought to myself i must be doing real damage so i stopped all together.
I do tons of stuff. Most everything is always 12 reps or under, standing or straight legged.
Just a couple examples from recently:
Standing Pull Down Abs
Straight leg sit ups
Hanging Leg Raises
Spread Eagle Sit-Ups
Swiss Ball Sit ups
Reverse Hypers
Band Good Mornings
Barbell Good Mornings
...the list goes on...
3x a week I'll do 4 sets of Reverse Hypers
4x a week I'll do 4 sets of abs
Those two are constants. I'll add in the extra good mornings if I need to really work on some soreness or to build even more strength/endurance in those muscles.