OP consider this, you may end up using more heat for a more desired straightness. And if you don't use more heat, the results may not be desirable.
Many will tell you, the blow dry is the key to great results.
Have you attempted blow drying in smaller sections?
im surprised no one mentioned roller setting. if you cant get the hang of the traditional way you can do a ponytail cheat set. the results give you hair that is super easy to flat iron and the hair comes out smooth and more moisturized as compared to blow drying.
This is the method I have been using for about a year and a half now.This was really helpful! Thanks~
@RegaLady
What are your current methods and products you use for straight hair. I like your avatar pic.