For compound curves which you mentioned you're having issues with. The trick is to leave extra so you can grab it....you don;t use an iron... (well i don't) on compound surfaces... rather.. pull and heat with your gun... this allows it stretch and be "pulled" onto the surface. It helps to have extra or a glove to keep the ot air off your hand. I like Ultra as its easiest to work with and will stretch a bit around comounds.. no wrinkles..