In this video I show how to do a Reverse Armbar from Closed Guard. This is a pretty common move that you see attempted throughout the ranks but finished with very little frequency. This is due to the fact that the setup is tedious and the hip movement required to dominate the shoulder is difficult.
This is a great move to attempt on someone who has no posture and will allow you to get a "1 under one over" grip. Take note of how my hand grip is. This is a VERY important detail. The arm that comes under the shoulder must be placed palm up with a gable grip. This allows you to pull down with your clenched fists while lifting up with your elbow (the one that bars the face). This is outlined in the video and I emphasize it, but I can not emphasize it enough. By controlling the shoulder and the head it allows you to open your legs and greatly move your hips out with little to no danger of having your guard passed.
Once I hip out I make sure to get that top knee on the back of the shoulder. My body knee does some transitioning too and it is optimal to have your knees almost squeezing on opposite sides of the shoulder. This is a difficult position to get to with a resisting opponent so I put more emphasis on brining that top knee over than the bottom knee under. I feel this gives my opponent less of an opportunity to resist.
Take note of the spacing between my opponent and my chest. This is something that is a little tricky. It takes a lot of reps to feel exactly where that pocket is and it is imperative that you get a lot of practice before you expect a successful tap. Until then you can transition into this position, attempt and then be ready to go to the Omoplata position.
I also have the "dream of genie" position. It is a little different than the way that most people do this. I have seen a lot of tutorials on blading the hand and coming across the back of the triceps to stop your opponent from turning their hand to the back of your head. You will find that if you turn your chest to the floor and squeeze in with this grip often you will not need to come across the back of the triceps (notice I said often, there will be times you go back to re-adjust).
Also it is important to note that if you turn your chest to the floor in the fashion that I am speaking it makes swinging that top leg over for the belly down armbar a million times easier (and now that I'm thinking about it I may make a video for that too).
Again I will say that this takes a lot of reps to get the feel off. Your best bet is to try it and if you are having difficultly ask someone in your class that is good at this move to help you with the finer points. This is one of those moves that regardless of how well I teach it, it will be difficult to grasp without being walked through it or having it done to you.