Prioritising means taking into account the ability of the umpire to handle change, the things that are most urgent and those that are easiest fixed. Coaches should be wary of coaching or even talking to an umpire at halftime. It can give wrong signals to both umpires and players. Coaching should be a discussion not a lecture. The answers will usually assist the coach in prioritising problems.
Nobody can turn an inexperienced umpire into an international overnight.
That is not the aim of coaching. Coaching should enable the umpire to move to or toward the next level. Remember coaching is about exposing people to ideas. Just as an umpire has to sell his decision to players, coaches have to sell their coaching ideas to the umpire. Body language, as well as being a good indicator of an umpire's state of mind is an excellent tool for handling players.