ive been working on my rolling harriers for a few weeks now and it is definetly a building process. You get one or two the first few times you try but you also blow a lot with incorrct entry or the wrong input. Then you go out one day and start stringing several rotations together before falling off and you arent blowing the entry as often. (this is where i am at the moment). then you will go out and start rolling as much as you want but maybe not in the direction you want. It is all in the timing and that only gets better as you attempt them more. Mine got better once i concentrated on doing what ever it took to keep the nose up in a high alpha attitude and realized that i was not working the rudder as hard in one direction as i was another. It also helps that my flying buddy would watch me and would try to observe what I was doing wrong/right. I don't think mixing out coupling in the harrier is as important because you are working the inputs quite hard, and fast, usually with the aileron pinned to max in one direction. Mixing out the coupling, however, is important for rolling circles but you are carring more speed with less inputs.