I starch at least 3 hours before I start working with whatever fabric I'm going to be using. I spray heavily, let it soak at least 2 hours, then I either air dry it or use the dryer, but I prefer the air dry, but sometimes it's just not doable because I simply don't have room to have fabric lying around. If you just spray and iron, you're just ironing the starch not the fabric, which is why your iron will begin to stick to the fabric and get all brown gunk on the iron, it's starch.