Q. I pass the guard and move into side control. But he's got good hip movement and is working his hips under mine to put me back into guard. What do I do?
A. Watch Dog Armbar
Q. How?
A. Watch Dog side control focuses on the hips and legs, compared to regular side control which focuses on the hips and upper body. Switching to Watch Dog will keep his legs from getting under yours and putting you back into guard.
However, you want to be thinking at least two steps ahead. So you get into side control and wait for him to try and slide his legs underneath. Keep an eye on his far arm so that you know where it is. Switch to Watch Dog to block his hips, then transition immediately to mount. Because he was keeping his hips low to slide them under yours, it will be easy to drag them down at the knee and step over them quickly for mount.
But don't just stop at mount. If he reacts quickly, then maybe he'll get a good bump or drop to disrupt your mount and try to put you back on the defensive. Keep attacking. Go right for that far side arm lock as soon as you clear the legs to get into mount.
Q. What if I miss?
A. At a minimum you should wind up in what Saulo calls the technical mount or S-mount. BJ Penn calls it the double attack position. You can still execute the armlock from here, as well as work to take the back.