Let's see if I can verbalize what Brian had me do.
He was very, very specific. Place the grip diagonally across the fingers. That part is difficult to describe. The next part was what gets the heel of the hand on there correctly. He had me raise my left thumb up like shooting a pistol. Then, with the thumb up, push the heel of the hand over to the right . The feeling is that the heel leads and the left wrist bends more than if you just let the heel go straight down onto the grip. Finally, bring the right thumb down into position. Of course, remember to then check your clubface using Brian's method of holding the left arm out in front of you.
I really think that if you get the grip on there so you can cock your wrist more easily, your swing will be just fine and a whole lot easier.
Let us know how it goes.