Like some of the posters above, I don't straighten on days that I wash my hair. Sometimes I straighten at the very end of the day so I don't have to do all that work the next day.
It often helps me to put it in tight French braids while it's wet, keeping it combed and smooth while braiding, and using some hair spray to keep the flyaways at bay. This helps straighten my roots, which can be harder to get to, as well as the back of my hair which is much more coarse. It also sets my part and partially straightens my hair. Then when it's dry, it's easier to straighten. I never give myself a blow-out; I'm terrible at it and don't like the results. I think I have too much hair for this to work on me. My hair is very thick on top of being curly.
I have found that coconut oil helps immensely when straightening my hair. I use it all the time, but I noticed after I started using it that it was easier to straighten. It seems to smooth the cuticle and help keep the frizzies and extra bulk at bay. My hair is so dry that I could use a ton of it and not look greasy.
When my combo curling/straightening iron died a few months ago, I bought a dedicated straightening iron for my bangs. It is a Remington that is keratin-infused. Not sure how or if that part actually works, but it does work well for straightening my hair. It has variable temperature settings. The default is 375* I think, but you can go up to 450* or down to 325*.
The key to using a straightening iron, or so I've heard, is to always keep it moving so as to not damage your hair. Sometimes it can take 3-4 passes of the iron to get my hair straight. It also helps to use a flat iron spray or other product to help protect against heat damage.