Bumping the Cutter

[PGCougar]

Coach here. I want to work with my kids at practice more on defending weakside cutters looking to penetrate the lane as they come ballside, commonly known as bumping the cutter. Since you can't deliberately bump, push, or displace, I could really use your help clarifying what you consider good D and what constitutes a block or push when defending the cutters.

Let's assume A1 has the ball on the right wing and A2 is on the left wing outside the arc. As the defender, B2 would be near or in the lane watching both A1 and A2 while defending A2. As A2 makes his move to cut across the lane, B2 should close the gap, ideally forcing A2 to divert his cut up and away from his intended path.

Do concepts of legal guarding position apply here? Or is it a matter of making sure B2 stays in front of A2's path at all times challenging for the pass with his arm in the passing lane? Lastly, how much contact if any is allowed and what keys do you look for as an official?

Thanks for the help in advance - I want to make sure we teach our kids right.