There are some easy ways to experience the coordinated movements the upper body makes to suppport the intent of the feet for the skis.
Standing still on the flats, with poles off the snow, roll the feet/skis up on edge together as far as possible allowing the body to move as needed to be able to create max edge angles with the feet/skis. You should notice a natural shaping of the body, or counter-balancing, in direct responce to the amount the lower legs are inclined. Everything uphill (what would be the inside of a turn) will be higher, hip, shoulder, hand, ear
This natural 'counter-balancing' of the upper body reflects the movements to be used from transition as the legs are lengthened into the power zone of the turn.
Rolling off those edges and across up onto the opposite ones produces the movements that release of upper body entering the transition and across the feet toward the inside of the next turn. A slight forward sweep of the leading hip gives effective direction to the strong inside half's leading role.
To anchor the timing, stand across a very slight slope, starting on the uphill edges and quickly transition an edge change toward downhill while maintaining balance as you lock into the downhill edges.
This whole process can be taken into motion by starting down the falline on green terrain and linking rhythmical railroad tracks while focusing on coordinating the upperbody to the lead movements of the feet through each edge change. When this can be done smoothly, dial up the terrain/speed and belly out the turns to generate some lateral G's to balance against.
To further test efficient coordination and timing of the upper/lower body movements, step on/off alteranating feet throughout each turn while balancing solidly on any edge at any time, and maintaining a smooth flow from turn to turn. If this easy the timing is good. If the upper body moves too fast, or too slow, it will be hard to step seamlessly from foot to foot without the body pitching in, or out.