The hook grip release is really just the thumb slipping out from under the 2-3 fingers and then resting back on top of them.
If you are actually letting go of your grip enough that it is becoming narrower on the catch, and doing it with 190#+, your OL career may be shortened drastically if the bar falls on your noggin.
More PVC and empty bar practice. I did long Burgener-style warm-ups to train the release into my technique. As I started doing it with real weights, sometimes I would forget and regress, then I'd simply remind myself to do it again next time.
Also, maybe your grip is set too wide?...