For me the curls last super long with no styling product when I use a straightener, but like I said, this method damages your hair more :(
My hair is also naturally pin straight so curling irons do practically nothing for my hair (I don't think I'm doing it wrong either). If they succeed in curling my hair at all, it doesn't stay curled for long.
I like this hairstyle particularly because it looks like normal curls in the front but in the back...surprise :p
Products:
Chi Iron Guard and that's it!