Multiplicity

I've noticed recently that Seb and I have noticeably different handwriting. That isn't a problem when we're just taking notes. But we get a lot of written work to hand in, and it's long - so we'll probably both have worked on any given piece. That causes distinct breaks in handwriting in the middle of the work, and we're - or at least I'm - worried that it will attract notice.
Does anyone know any methods of making the difference less obvious?