For me the best time to straighten my hair is on a wash day after a good DC, I think I get better results and it lasts for a good amount of time (as long as I wear my scarf). I try to straighten on the lowest heat possible but that will also give me the desired effect, it also helps if I straighten in small sections, I only use heat protectant before straightening. This is what I do if I'm doing it properly, it can take me anything from 45 mins to an hour and a half depending on how small the sections are.