Well it sure ain't common sense to pull back with one hand while keeping your back straight and " the handle is for positioning " really ? I adjust the " position "of the handle for comfort when using the wand and while it's occasionally pulled back with one hand, eg, when wanding under a snooker table or similar, my left hand is on the handle when working, not pressing down or forcing in any way, just spreading the load on the back muscles
The timing of trigger depressing / releasing is fine but the body mechanics is wrong.