Learning to brace and breath properly ? (Squat)

[Sqbero]

I've been training for a couple months , newbie at the barbell. h
Had never done a squat in my life (lived a sedentary lifestyle) until recently.
I made good progress on just focusing on the movement.
I watched a video that said I need to brace my core. Breath properly.
I'm trying the whole breathing in with diaphram , bracing the abs.
No more progress since I started that and I don't see any extra stability from tightening my abs.. I'm still progressing in my other lifts which I'm not using that technique on.
I actually feel more winded than my old method of breathing in going down , out going up.

Any advice? Has anyone had the same issues and how did you fix it?
I think I may have issues using my core or abs effectively , I can't do a single situp or any ab exercise without it hurting my lower back,. I've put in 100s of hours trying it's never worked despite trying all the cues. I can however, do over my body weight in lbs on all major lifts. And doesn't bother my lower back much on the lifts.

I don't have much money for a coach. Thanks for any advice.

[SuffolkPunch]

It's very unlikely that core bracing becomes the weak point in your movement when you are new - get better at squatting just by doing more squatting. Following a routine with planned progression will be good (any of the ones in the sticky threads)

But it's still good to learn about bracing...

There are videos in the Exercises section sticky threads. There is also the strongerbyscience "how to squat" article. Also, anything by Calgary Barbell or Alan Thrall is going to be good.

You could get yourself a belt which makes the process easier. You simply take a big breath and push your abs against the belt.

[Garage Rat]

Work on doing "hard style planks".
It will teach you to use the core/body together with tension.
Research the "valsalva manuver"it may help with the way you brace your core.
Bracing is important as it helps with creating tension throughout the body which helps with strength and maintaining good technique.
As for mid section work you might try sit up over a BOSU or stability ball that supports the back as you sit up.
Hanging knee raise shouldn't hurt your back as well as kneeling cable crunches.
If none of this works for you i would get a coach or qualified trainer to help you out in this area.