My comp is broken so I cant view his videos to post it but he traps the under hook with his elbow and grabs the overhook and peels the arm off of the shoulder to get rid of the seat belt and then bridges hard to the underhook side to get his same shoulder to the mat by the dudes face then granby. It gets you either right out or into guard on the top if the guy holds it tight.
He has a couple different escapes that start the same way