i had that problem too - my hair reverts easily if there is any hint of moisture in the air!
my process is as follows:
1) wash and deep condition hair for 15-25 minutes w/Trader Joe's Nourish shampoo and conditioner (i use a cap but i don't sit under a dryer), then detangle with wide-tooth comb and rinse.
2) add Wild Growth Oil, detangle with smaller-toothed comb and braid hair into about 12 sections, let dry overnight. you can blowdry if you want, i just suggest using a heat protectant before doing so. i'm just lazy so i divide the process up into 2 days.
3) take down one braid at a time starting from the back of my head, spray with Silk Elements heat protectant (forget the exact name), straighten with CHI knockoff from Sally's. i do use a pocket comb at this point for the ends, if you have a rattail that works too but i just refuse to buy one, LOL!
4) immediately after pressing a small section to desired straightness, i take a tiny dollop of Aveda's Anti-Humectant Pomade, rub between my fingers, and distribute to straightened section.
this stuff works wonders, i promise you! too little won't get desired results, hence why i put it on every piece i straighten instead of waiting until i'm completely finished to just apply to my entire head. but too much will make your hair kinda heavy and greasy-feeling, so keep that in mind if you want "swingy" hair.
5) wrap at night, unwrap in the morning, enjoy straight hair for another day!
***when i went to get my hair trimmed this past weekend, the stylist used Redken products to wash and condition, and a leave-in conditioner that kinda pulled my texture a little less coily (not a lot, just a little). i think it's called Smooth-Down or something like that... i know it's probably pricey but i did love it! and she used Mizani products to blowdry and flat iron - a heat protectant, pomade and anti-humectant spray. i didn't feel the anti-humectant spray worked nearly as well as Aveda's though... but that's just IMO.
hope some of this info helps!