I used to have a really tough time in this position but now I have three sweeps that I use, two really effectively.
The main thing I look for if my opponent wont let me push him down towards my hips is a deep hook on his top arm. If you were on the side they filmed the video above then you would be looking to take your left and come underneath his right arm, hooking at the elbow (by underneath I mean between his arm and his rib cage). From there you yank it back and gable grip your hands together and you've established a really powerful control over his body. The arm is actually fairly easy to catch as your opponent is often using his hand to push down on your top knee and set up the pass. From there, there are a few ways to sweep him but its almost pointless to just describe them and I dont know of any videos (this was shown to me in person). Just try to establish that position I described and you'll have some good ideas on where to take him.