Java introduced this drill to my DD 3 weeks ago and it almost immediately fixed her timing. We had tried all of the above over the last 2 years and nothing stuck, mental block. She took this drill and incorporated it into a full delivery; her posture improved and her ability to locate improved...
We try to mix it up each time. The variety keeps it fresh and interesting. My DD is 11 so I don't let her set the whole plan. She will pick something(s) she likes to work on and I will pick something(s) her coach recommended in the last few sessions.