Hi there,
I definitely relate to being in the place "just before you see"
Because that is where you are at, I think. You stopped blindly believing (if you ever were) and are questioning what it is the "experts" are talking about. Congratulations!
(Of course I am also just learning this too, so please, anyone - let me know where my knowledge is lacking etc...)
Few suggestions for you:
1) stop thinking that it is incredibly complicated
2) make sure you have a working knowledge of the horse's anatomy - you can picture his bones and maybe even the major muscle groups by looking at a horse
3) it really helps to kind of superimpose a drawing of the horse's skeleton - even a very basic one - like if he was a "stick horse". The important parts would be: the complete hind leg up to the hip, the pelvis. the spine all the way to the head.
4) begin at the halt. figure out how your horse is standing - paying attention to all the parts important to true collection (you mention being familiar with the theory)
...it literally happens like the books say...
5) you can try and play around with finding out the mobility in the horse's body by the following exercises (of course use common sense about not crossing any comfort lines with the horse and paying the price...
)
to look at the raising of the back - use pressure on the underneath of the horse's belly (mid-line or so) - experiment with location/pressure to get him to lift his back (or wait 'till he has a bowel movement and observe...)
to look at raising the forehand - pressure on the sternum - again, play around to get a result
for the pelvic tilt - put pressure on his haunches, usually beginning both sides of the top of the croup (standing behind the horse) applying pressure downwards, kind of digging into the muscles there - there is a spot where most horses will tuck their pelvis. Not saying this is exactly what you are looking for, but it's kind of neat to observe the mobility.
you could probably have a good conversation with a qualified equine body worker about this...
6) for observation of moving horses - it sometimes helps to focus on the Lumbar-sacral joint as well as the 4 joints of the hind leg. In some horses, it's almost like the LS "opens" instead of the pelvis tucking under - it seems like you can see a clear hinge there - with the croup flattening and hind legs obviously trailing. (not collection)
once again, trust yourself to see it. Think in simple terms and look for the bones
I just remembered - this site helped me tons:
http://www.sustainabledressage.net/collection/true_collection.phpthere is tons more when you begin to see the muscles, but hope this helps for now?
A great topic, by the way, I would love to learn more about this as well...