After over 3 years of trying to figure this out I feel that the most "realistic" banners (banners which look most like scale fabric) are hand painted onto kleanex tissue - it wrinkles much like fabric! Paint the tissue the desired main color, let dry completely - then add details! You'd really be amazed at what you can do with just a little practice! :)

Just get a tissue, paint a few banner shaped squares on it and let it dry totally. Then come back the next day (the tissue has to be TOTALLY dry!) and carefully cut out the ones that you feel have the best "wrinkles" and begin painting your design on them! It makes each banner a true artwork, unique unto itself, and something that you'll be proud to say you did on your own :)

You can do it! Just make a few for practice and you'll see how easy it really is! 

~ Brother Edward