I don't have any tips for you. My hair is also shoulder length- but so thin you can almost see my scalp. Just kidding- but it's pretty fine so I just put it in a ponytail and cram the tail in the cap. I have no trouble getting it all in there- in fact- I might have some extra room for your hair, too.

Braiding might work or a ponytail.

Surely someone has some good tips!