I found when using 2 hand grip, in addition to the somewhat isometric technique, is to grip 70% (thereabouts) with my left hand around my right hand which grips the firearm. Concentrate pulling the trigger straight back.
If you try to squeeze the trigger while at the same time gripping the gun too much, you will torque the gun. These muscles go together. Thus you must relax the right hand grip (relative to the left hand) so your trigger finger will not cause your hands/forearm muscles to move the way they want.
Try holding a hair brush, extend your arm, tip it forward a little, then squeeze it, watch it move.

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Marty 4513TSW 13-1 642 60-10