My best suggestion is to do grip holds. Grab heavy weight(for you the 80's or so) and just stand and hold them. Try doing 20-30 second holds. Then progress up in weight if you can. Stay near the rack so you can put them back in a hurry or set them on a bench so you aren't dropping them. For now you can try using straps until your grip catches up but use them only when your grip is failing.
There isn't a big cosmic mystery on grip as many people think. Grip strength works the same as everything else. If you want to bench heavy you use heavy weight, if you want to squat heavy you use heavy weight, so if you want to hold heavy weight then you hold heavy weight.
Cheers,
Scotsman