In our warmups, we use a simple 'pushing' kick as a way to limber and warm up the leg and hip muscles. It looks like a heel kick but is done pretty much in slow-mo, and pushes outward at groin height with the flat of the foot.
Right foot pushes, right hand goes forward. Left foot pushes, left foot goes forward. Not very difficult.
My comment last night was to make sure that the elbow goes across the body and covers the center line. Meaning when you're pushing with the right, you're not just covering your chest or neck area with your fist. You are attempting to bring your whole forearm across from the side so that it is vertical and lines up between your solar plexus and your opponent. In this position it is far greater that you will be able to counter the fastest kicks sent to you in retaliation.