Hey, I only just got to read this thread. It's great that you've figured out how the draw the hair in that pose, but I suggest drawing some head bases and practicing all different types of hair in all different poses. I think that one of your biggests problems is that you think of hair by the strands, instead of as a mass, with some small strands coming off.

Here's a good tutorial to help with your hair's looseness:
http://www.angelthesis.com/index.php/the-head/4-5-hair