A few questions - 1. How much do you weigh (I won't judge, I'm 250 right now - going down but still not where I want to be)? 2. What brand/model/size ski do you have? 3. What type of handle are you using? 4. What type of glove are you using?
I had a very embarrassing time at a private ski lake a couple of months ago. I had a new pair of MasterLine ProLocks (similar to the Radar Vice above). No matter what I did I could not hang on to a handle at all. It felt like everything was covered in soap. So, I came here and quickly got a reply that when using a new pair ProLocks the strap needs to be sanded first. When brand new the strap is too smooth and slick. I got out my sandpaper and it completely fixed the problem. I have much better traction now. Also, I skied like crazy this summer and have a lot more strength in my shoulders, arms and hands. Exercise helps.
Finally, do work on the techniques mentioned above. Even at 250 I can pop out of the water pretty quick now with better technique. Stay tight, knees in, pressure on my front toes. Just FYI - Double boot/Radar Senate/71".