One of the problems that many have with starch is they spray too heavily (get the fabric too wet) and press too quickly so the starch doesn't have time to absorb into the fibers of the fabric. You are more likely to get distortion this way in addition to flakes and gunk on your iron.
When I starch I spray lightly and gently roll the pieces up and put them in a plastic bag to mellow out a bit. This is much like was done back in the day when clothes were sprinkled and then ironed. Anyone remember putting sprinkled clothes in the fridge if you couldn't get to them right away? When the starch has fully absorbed into the fabric it won't be wet but will be some damp. Gently press, not iron, to set the starch. Pressing is putting the dry iron down and then picking it up to move it rather than sliding it over the fabric which is ironing. I find if I do it this way fabric doesn't stretch and my iron and board stays much cleaner.
If your iron gets gunky from the starch use a moist magic eraser (like Mr Clean brand but any brand will do) on a cold iron. Works great to get the gunk off. I have a shiny sole plate on my iron and it's not teflon coated so don't know how the eraser would work on that. Perhaps someone who has that type of iron could advise on this.