There are a few important details to pay attention to on the Hip Bump sweep:
1- The correct situation to use this sweep is when your opponent is posturing up strongly inside your closed guard and is preparing to open your legs. It is challenging to do the Hip Bump if your opponent is pressuring forwards.
2 - Control your opponent's elbow. The most common reason this sweep fails is that the guard player could not control the opponent's arm, and they were able to post out with their free arm and block the sweep attempt.
This next guard technique takes advantage of the opponent's defensive reaction of posting their arm to stop the sweep.