So I've been able to really make progress on mediums with my haflinger gelding this year, who I thought might never be able to truly do it. Here is what worked well for us.
1. Not hill work, but hill lengthenings. Point him towards the barn or somewhere he wants to go and ask for the lengthening up a hill. When doing this, DO NOT give up the connection. He must stay connected in the bridle and that must help keep the forehand up while the hind end propels under him. In the beginning you might need a far stronger rein connection that you would want at a later stage.
2. Intermix half halt go half halt go half halt go when you are on the flat. This never helped us produce an actual lengthening like the hill work did, but it did let him know that when I put both my leg aids on in a "squeezing the ketchup out of the bottle" motion, I'm looking for this power and up forward motion.
3. Once you are getting something that feels like a lengthening/medium up a hill, then do it in the arena and do it going towards somewhere he wants to go. I finish all of my rides with a big medium back to the barn. The "up" excitement of going somewhere the horse wants to go helps to produce the necessary forward, but up energy you need.
Some things i've also found:
I thought doing a big half halt in the corner and then pushing him forward would work, but that really doesn't help me, it seems better to maintain momentum around the corner and then sent him out of that.
If they are going to come off the connection, better that they come above and up than low or behind. Low will just produce low.
If your reins are too long, a medium won't happen.
For us now, it's a matter of slowing things back down a hair. My boy, unlike a TB wants to be slow and lazy, so we did have to add speed to accomplish this. We now have the hind end engagement and he is showing should freedom up front, but we are still a hair over-tempo. So, now I'm working on producing a tempo that gives him a hair more air time to work with.
I literally thought we would never have a medium/lengthening, so if we can do it, you can do it! Keep faith!
