The key to gliding and skiing is a mixture of two things; one, proper balance helps a lot, but it doesn't need to be "perfect". Skiing itself is a pretty smooth motion (compared to running/walking) so don't spend hours trying to balance your glidecam perfect.
Two its all about practice, it took me a good 2-3 years to really nail my glidecam work on skis and I went a couple years without filming much skiing on my glidecam and it took me another season to get back into it. You have to grip your glidecam much more than you'd think skiing, especially filming jumps. It's all about driving the rig, you'll eventually start to know exactly where its aiming, I can just cruise at any speed and I know what my shot looks like, but I've been using a glidecam for 7 years. Its all about practice, practice, practice.