At least I'm pretty sure it's Charuto.
Charuto--real name Renato Verissimo--is one of BJ Penn's top jiu jitsu instructors. I've been looking for this video for days after first stumbling across it over at BJ Penn.com.
The tip is how to draw out and isolate the arm in preparation for an armlock from the guard. Charuto's point is that if you just grab the arm and stretch it, you make two mistakes: (1) if the arm is straight, then it is easier for the guy to just pull it out of your grip and (2) if you just grab the arm and try to pin it, then you will give away the fact that you are going for the armlock.Charuto has you bring the wrist straight forward toward you, while pulling with your legs to help break posture. Then swing the arm across your body. But as you do so, come across with your other arm and bring it down across the inside of the guy's elbow. This will create the kind of bend in the arm that is necessary to keep it trapped as well as to hold off telegraphing the armlock until the last minute.
