I use three techniques after the guard opens.
A. Double underhook
B. Sprawl out, shutting the legs down
C. Knee cut across to either direction.
D. Backing out and standing up with knee control
Those are in no particular order. Which one I use depends on their response. If I open their guard, I use whichever I'm most comfortable with. If THEY open their guard, I scramble, using the one needed to defend against their attack.
Now, to open the guard, I usually insist on one of the basic passes kneeling that you should already know. For example, stiff arming the chest and hip. Then I work my standing passes, checking to see if they have a strong sweep game. If those basics don't work, and the situation is dire, I bust out the "Gracie Gift". That'll get that guard open because they start looking at you like an idiot and scheming on that triangle. I then pass immediately.
I'm a white belt though, and my shit only works up to mid level blues, and usually not that high, so take that for what its worth.