I spent two years trying to perfect the hang technique in high school and I was an utter failure. I was fast and tall so was sent to do the long jump, but ended up being a little too big to make this technique effective. There were a lot of 5th place finishes in my future at meets.
The key to the hang technique is the short step at the end - think about double jump basketball jump. This allows you more vertical velocity with just a small decrease in horizontal velocity.
When you hit the air with this greater upward momentum it is taught to stand tall, legs back and then knees to chest before legs are extended. There are a lot of moving parts and it requires a certain amount of flexibility (another major issue I had). Alas I had trouble just doing the last step, as this causes the greatest hang effect.
Please refer to this paper on the hang technique. I also suggest while learning that you focus on the takeoff and then work your way through the steps.