my mom taught me to clean my iron using salt. Spread out a newspaper, sprinkle with salt and then run the cold iron all around on top of the newspaper. Takes off the crusties pretty well.
So far since using the spray starch I haven't had a buildup. But I also haven't been doing this very long.
BTW have to brag about my iron. Found a high end Rowenta iron at the thrift store. The burst of steam button is broken but otherwise it works like a dream. Had some burned on crusties and cleaned those off. And I only paid $5 for it!!