Try Rennies suggestion next time you need a release.
I saw this in action a while back and was dumbfounded to see how quickly the snake let go when a short sharp burst of air was directed into the mouth.
The snake immediately let go and I swear, if it had eyelids, it would have blinked in confusion.
I have since had occassion to try it myself and have been constantly impressed.
On your hand, where you have the crease of skin at the corner of the snakes mouth, is the gap you need to direct the air into. A good hard blow will have it releasing you rapidly.