Improving push passing speed
To beef up your players passing this session improves their technique (transfer of weight etc) to push pass with greater power so their passes reach their target, even under match-conditions.
Why this works
Pushing is faster over short distances as there is no backswing. Your players may have also become aware in previous sessions of the opportunity to disguise passes. Disguise causes players to run (or place their weight) in the wrong direction and ultimately leads to hesitation in defenders reactions because they uncertain of which way the pass is going.
Slapping (slinging) is an essential technique for retaining possession but should be used as a cross field pass (eg. passing at the back) as means of transferring the ball from a crowded zone to space. Slapping in crowded zones is poor technique: it is too slow in terms of preparation and backswing which is why coaching the push pass is so important.