This has been on my mind forever and I am constantly looking for ways to expand my teaching repertoire so I can get through to the minds of my riders and help them to learn 'the feel for the horse'. I got to the point that I would ride a particular movement myself and then dissect it in my head so I knew exactly what I had done, when and for how long. It is not always easy as there are moments that my subconscious tells me 'you half-halted' and yet I feel almost no reaction in my body and plenty of reaction in the horse! That is how I differentiate the most difficult elements to teach from those that are passable. If I cannot do an inventory of reactions involved in a particular movement/ aid I classify that aid as highly skilled and almost always self-taught. If I can, then I would insist on all the riders to learn it through hard work!
I am currently ploughing through Human Anatomy and physiology books which seems to help when it comes to explanations. My favourite anatomy focused equestrian book is called 'Balance in Movement' by Susanne Von Dietze - could be read over and over.
Now, if only I can get R. away from in front of the TV so I can watch show jumping Super League from La Baule, France I would be well pleased!