Well, i may have an idea for that. A collaborative post on piratepad. Instead of going back and forth with separate posts, you and another player both come online on piratepad at the same time and work together to write the interaction between your characters. When done, you do the same with the next person. When you've had all the characters, you copy the whole wall of text and submit it as one post. I've done it before and it could potentially save a lot of time.