Same as Rye, doing both is alot better. I used to just straighten mine, and It was always poofy, and it never stayed how I wanted it too.

You blow dry down, at the same time as you run the brush through it, thats what I always do. It dosn't get rid of the frizz, not for me anyway , so I then straighten it. Before straightning, if you have thick hair tie the top half in a bobble and straighten the underneath first, its also really helpful if you put some sort of Serum on.

Ive used straighters for 3 years, and Ive never singed my hair, mine go up to 200. I have burnt my fingers many times. I always run my hand through my hair straight after straightning it, thats painful. xD

I usually repeat this 2 times a day. My hair is awfully thick, and curls 10 minutes after straightning.
But I should (hopefully, they are expensive) be getting some GHD ones that are the King of straightners, and go over 200