The bounce of your sand wedge is designed to allow the club to slide through the sand instead of digging down to take a divot. Ideally you want the ball to fly out of the bunker like a piece of sand, with out actually contacting the golf ball. In order to use the bounce effectively you must have the proper set up.
Club should travel back along the body line ( outside ) Set the wrists in the backswing so that the clubface remains open and will stay open through impact. Clubhead should enter the sand at the point you were staring (2 inches behind the ball) and accelerate through impact on the body line (inside path) maintain the slightly open clubface. Body Rotates to a full finish!
Set up with the clubface closed, using the full swing grip… this creates a digging leading edge. To get the ball out of the buried lie. Align the body square to the target with the weight slightly on the front foot… this is to premote a descending blow. The ball should be slightly forward of center. Levitate the clubhead over the point in which you are focused on the club entering the sand.