I recently learned from my hair stylist that hairspray can be sprayed on your hair before using a flat iron rather than using a special heat protection product.  I tried hairspray and it worked very well.  My hair, which normally is on the curly side, was straightened and soft.  I’d always bought heat protection sprays for use with my flat iron in the past.  But, hairspray seems to work just as well.  It’s nice to have one less hair product to buy.  Try it!