Faultless makes a good iron cleaner. You might try laying down a layer of salt or sand (do not try this with sugar) on a piece of newspaper or paper bag and iron over it. The abrasive surface might help clear the surface (as long as it doesn't have a special non-stick coating). I've never been very lucky getting the adhesive off fabrics. I always use a scrap piece of muslin or duck cloth on top of my ironing surface just in case.