Winter Exercises to Improve Jumping [without jumping]?

So, I can't jump outside of lessons for the time being -- a. I'm not totally comfortable doing that with Sasha yet, and b. Barn rules say that I can't without an instructors permission. Alright, I can still do poles and the such.

Sash can be a bit "up" when jumping sometimes. She's usually ok to the jump, but she gets excited after. She has been getting much better, but I want to improve. Sash needs work slowing her canter down after the jump and staying relaxed. She will halt after the jump with no problem, but she [at least] tries to go quickly after the jump.

Any exercises I can work on? I'm assuming collection/lengthening work will help, and I have been working on that, as well as working on a very loose rein on occasion to just let her relax and stretch out.

Thanks!

How about canter poles?

Long and loose ALWAYS help. Lots of transitions, etc. are also helpful. Bending, circles, etc.

I'm not a jumper, but those should help in general. I'll let a jumper chime in on what will really improve jumping.

Place two poles either 36' or 48' apart. Practice adjusting your horse's stride by getting 3 strides, then 4 strides, etc. This exercise will help improve your ability to adjust your horse's stride.