Assuming your beginning from the back with an over-under...
Lets say your left arm is around his neck and your right is under his right arm pit. As you said, use your right hand to trap his right hand on his belly, leg over BOTH yours and his hand, lock up your legs and squeeze (Be sure you ankles are high on his belly, NOT near his crotch... You'll get yourself ankle locked there). Slip your right hand out, slip it over his right shoulder and marry to your left hand with a gable grip (Left hand knuckles towards the ceiling, thumb towards yourself. And right palm up, knuckles near his collar bone.... NOW, swing your right elbow behind his back and LEVER your left arm across for the Dan severn/Jay Leno. Your right elbow should be aligned with his spin here, Once your left elbow is alligned with his chin you'll be unstoppable. Usually you'll not have to release or change your grip at all. Small hint... ARCH your back while all of this gabling and levering is goin on... It's key