When I wrote (purely for fun) it was sometimes with a friend. If I got stuck I'd pass the work off to him/her. Since we both developed the story together, it was sometimes beneficial to let the other person write until they were stuck and share back and forth.

Writing something with the opposite sex also gives the work a unique blend.

Unless this story is very personal, you could try talking to a friend about it and seeing if they want to jump on board. Even if they don't want to write, friends are great people to abuse horribly by bouncing ideas off of them over some coffee or sushi.