Any fabric I'm going to work with, I spray starch heavily on the right side of the fabric, put the fabric/s in a plastic bag, and let it sit for a minimum of 2 hours, then I either let it air dry or stick in the dryer for a few minutes, then iron on the wrong side of the fabric. If you do it this way, you very, very rarely will get flaking and your iron won't get all gunky, and consequently, neither will your ironing board. The reason your iron gets all gunky is that the starch hasn't "gotten" into the fabric fibers and you're really only ironing the starch and not the fabric. I also use the concentrated spray starch and mix it 50/50 in a spray bottle, it goes a lot further than the canned starch.