You simply have to keep doing the session once per week and you will notice yourself getting better at the faster speeds and doing them easier as time goes on. Remember, once you become elite, it takes a long time to keep getting those extra little performance increases. From there on, it just takes time. Further progress from an elite level usually never happens, so the Cannonball Athletic Coordination Drill will prove that it is possible. Be patient, train hard, smart and results will follow.
What you do once you can complete the session fully without missing a beat?
Once you can do the entire session properly, you should have elite abilities in the vital specific fitness components for the sport you play.