I used to use spray starch, but decided to try the fabric stiffener from Michaels and it works GREAT. It is called Stiffen Stuff. Its around $7, but I always use one of my 40% off coupons when I buy it. It is very stiff at first and eventually gets softer with wear, but it has a great result and I have found that even after tons of wear it will still hold its shape so well. It is kinda of a pain because the nozzle gets clogged very easily so be sure to rinse off the nozzle with hot water after every time you use it. I sometimes forget and it will unclog after running through hot water for a while, but makes it harder if you do that. It is an 8 oz. bottle, but you really dont have to use alot. I have done 100's of bows with just one bottle. HTH!
Also, the Stiffen Stuff dries so fast. I usually put mine under the hair drier just because I am usually rushed during the drying process, but even if you leave it out on the counter or somewhere it will be dry within an hour or less.