Artemis BJJ (Impact Gym), Can Sönmez, Bristol, UK - 12/08/2014
To pass the open guard, it is advisable to grip on the inside of both their knees for control (though not everyone would agree on that: others suggest gripping lower on the trousers by their shin, knuckles facing forward, or even at the bottom of the trousers). The main danger is that they will try to loop their leg over your arm, which you can mitigate by gripping a little lower than the knee. If their legs are raised, twist your elbows in, so that your forearms are parallel to their lower legs. Be sure to keep your elbows inside their knees: if they do manage to loop an arm, you may need to release and then regrip back inside their knee.
That means you can then start to move their legs in several directions. There are many variations of the bullfighter pass (also called the toreador, toreana, toreada, toreando and matador, among other names. Google tells me the Portuguese for bullfighter is in fact 'toureiro'), but I think the simplest is to step back when you have that grip, so that the soles of their feet press into the floor. Straighten your arms and lean through them, so that all your weight is punching downwards towards the mat.
The aim is to prevent them being able to move their legs, so that you can now walk around before they are able to recover. As soon as you get past their knees, drop your leading shoulder into their hip, falling forward. Maintain at least one grip on their leg, as otherwise they may be able to start to recover by getting a leg in the way. Your next priority is to block their hips, so release one grip in order to bring an elbow around their far hip. Drive your near knee into their near hip, then move up into side control.
Teaching Notes: I had a reminder tonight that not everyone comes in a gi to Impact Gym (as a lot of the students come straight from an MMA class), so I was trying to think of the nogi application. It's possible to do it just pushing on the knees, but nowhere near as effective. Holding the ankles might be an alternative: I'll have to play with it more. Or better, I just need to make sure to have a few pairs of spare gi trousers to hand (especially for what I'm teaching on Thursday, as that version is even more gi dependent). ;)