That's definitely a good thing to feel comfortable on your back. But I wouldn't go as far as to pull guard in mma. It's just too risky.
From inside my guard I usually control the head and keep their posture down. The first thing I look for is the triangle. Next I'll try and see if I could pull off any sweeps. After going threw those two options I'll start looking at all my other subs. There's also a neat little trick to cause some serious pain to your opponents ribs just by using your knees, I've even seen people tap from it.
While inside someone else's guard in mma I try and give them a few punches before going for the pass. Just recently I've found a new love for leg locks. When I'm doing mma I try and control the hips and throw fast, short, snappy punches. I try not to get carried away with flaring my arms out too wide, but that is a bad habit that I need to break. My favorite pass is definitely the double under hook. If they roll out you have them in a body lock or if they fight it they just end up having their guard pass.
Considering the knees to the thigh/butt while on top, wouldn't that make you more susceptible for a sweep? I mean, if your partner had really good timing. Or were you thinking of a shorter strike?
"The battle is won or lost far away from witnesses--behind the lines, in the gym, and out there on the road, long before I dance under those lights."