Transitioning from X Guard to the Back can be both awesome and difficult. In this video I show you the finer points of this transition so that you can hit it with higher success.
The first roadblock on your way to the back is going to passing the leg over your head. This leg (the one by your ear) can be either extremely easy to move or extremely difficult, I find that my students have very little "grey" area with it.
Passing the leg over the head is a combination of pushing and lifting between your two legs. If you reference the video you will see how I get my opponent light on that foot by the head. This will take some practice but once you figure it out, it allows you a lot of control from the X Guard position.
After passing the leg in front of the head I take my hand and feed it to the belt. I DO NOT let go of my grip on the far arm. This keeps my opponent bent over and their base/posture broken. Now that I have my partner in this awful position it's time to take advantage of them. I do this by taking my free hand and grabbing the belt.
After getting the belt I can now leg go of the sleeve grip and immedately transfer it behind the knee. This is the piece that most people miss. By placing my hand on the back of the knee it gives me the ability to chalk my opponents leg so that I can make the little transition to the back. You should have plenty of time to get your shin to the back of your opponents knee.
Now all you have to do is take your free hand and grab the belt (both hands are on the belt at this point) and pull backwards while pushing out with your legs. This last transition where your opponent falls to the floor takes some getting used to. After you practice it for awhile it will be a very smooth transition that allows you enough time to both get your hooks and a hand in the collar.