It depends on how soft and good you have your horse at disengaging his hindquarters. If you have to do all of it then it should take you a good hour the first time and then over two weeks 20 min of each ride (6 rides) of "playing" with it and then you should be pretty good at it. If you send a video to me I can help you tell you better how long and where you are at in the process :) You can send it to my facebook page which is Brandi Lyons Horse Training or my group page is Brandi Lyons No Limits Group or email to me at info@lyonsnolimits.com:) After you get it without distraction then you add distraction like doing it on a tarp or on a bridge or in a hula hoop... that becomes fun ;)
