For a really, really hepful on the explanation of the Documentary Hypothesis check out pgs. 101-103 of Bruce Feiler's Walking the Bible: A Journey by Land through the Five Books of Moses. New York: Harper Perennial, 2001. This book is super enjoyable and so educational. Makes you really feel as if you are THERE in the Holy Land.
Here are some cartoons that I think are hilarious that relate to this lesson (though not exactly the tone I use for the flyer) but I don't think I can easily get permission to use them on the flyer so I'll just link to them. Enjoy!