It seems to me that given the idea of action/reaction, the basic pummeling technique should be a rocking, swimming sort of motion, almost like playing an accordian. To set up the reaction, given what Martell says here, and not what I was thinking recently, you would push with your underhook and pull with your free arm. When he reacts by trying to posture up, you would pull with your underhook and push your far side forward, swimming your free arm into the space between his arm and body.
As you do this, I'm thinking that you want to squeeze your arms in, elbows first, then as you bring the free forearm tight, do the "good to go" swimming motion with your hand to hook into the space created between the guy's arm and body as you change direction.
I think this would work well combined with a simply outside trip/foot sweep on the underhook side. If you get a good tug on the underhook side, ducking down and to the outside, putting your outside foot right next to the guy's foot sets up a dangerous takedown. If he doesn't react to restore his balance, then there's a good chance that he goes down.
The idea is that while he is focused on his balance he is not as likely to keep his other arm tight against his body. It is more likely to fan out to help restore his balance.
This is at least what I want to try next time we're doing pummeling drills. I've got to get the guy to want to move his arm, rather than just trying to drive my arm like a wedge between his arm and body.
I always try to think that somewhere out there is a 120-lb expert in pummeling who would have no problem getting double underhooks on me and my training partners. Then I ask myself: what is that guy (or gal) doing, technique-wise, that I am not doing? What is it that will seem so obvious once I figure it out?
