I have a little story for you that you might find interesting.
This technique does work because it calms the animal down and almost makes it impossible to reel back and strike properly.

I have a professor who is a Herpetologist (he's also a lawyer and a lot of other things, but he discovered a species of mud turtle). One day he was telling me that he was field herping a little bit, and he saw a snake under a board. He thought at first glance it was a little rat snake, so he lifted the board really fast and quickly put his hand over the snakes head.
Turns out, that snake was a young cottonmouth. He realized this immediately when his hand was on the head of the snake. The snake was coiled up with it's head laying in the middle of it's coils, and made no attempt to escape.
With a fast hand and a little prayer, he figured that the best option would be to pull his hand away as fast as possible, faster than the snake could strike.
He manage to do it, and wasn't bitten. But he said a snake will rarely be able to bite you if you have your hand on their head, because due to instinct they feel they need to strike from a slight distance.