I generally tell my skiers that they should use poles that are shorter than used for classic skiing. My rule of thump is mid bicep. Anything longer and you generally don't get good follow through with the poles. Shorter than this and they just get in the way and don't add a lot to the "propulsion" up the hill.
We tend to do three types of ski walking/bounding. The first (the ski walking) is used for technique work, to keep heart rate down during L1 or, if faster, for Level 3 work. With the lower body, I try to focus on good forward lean, open hips, and keeping your kick legs under you (as opposed to over striding and heel striking). There is a little pop with each step to keep us honest with technique, but only really serves to help with weight shift. With the upper body, I focus on a good pendulum swing of the arms, hand position at point of contact, and engaging the lats. This is definitely not just race walking with poles.
The second is ski bounding where the pop from "setting the wax" is much more pronounced. So much so that you do indeed leave the ground with the "glide phase" being the time spent in the air. We tend to use this for Level 4 work or following Spenst.
The last is Spenst. These are short rep, high explosion movements. Typically 3 sets of 10 kicks on each side or so with long rest in between efforts where you really try to bound as hard and far as you can. This is a neuromuscular development tool, not for conditioning. Chris Grover has a great article on it in Master Skier from a few years back.
Hope this helps.
Dan Voisin
