I have ridiculously curly, thick, FINE frizzy hair. To the point where strangers molest my head in public, because it goes past my **** and is .5" shiny healthy spirals. People ask me constantly if its real/pull it to see how fast it springs back into place. My hair needs so much moisture on a regular basis that I literally have never ever experienced greasy hair in my whole life. Hairdressers say they have never seen such real curly hair in their whole careers (and then proceed to butcher it). Sooo I definitely understand straightening pains, I couldn't straighten for YEARS because I just couldn't get it sleek. I *love* straight hair, it's so sexy.
Here's the end all strategy to making your hair be your bitch. I'm an expert at this and I feel for you. Everyone should be entitled to sexy hair

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To wash:
- Avoid shampoo. Your hair is too curly to need this, you're actually abusing it by doing it often. Twice a week at most. Find something as simple as possible, detergent is not good for your hair. It'll only take like two weeks for you to start noticing the significant avoiding shampoo makes. I like head&shoulders because it makes the hair a bit softer than the simpler brands, but I technically shouldn't.
- Always use conditioner. Do this every time you shower. You can "wash" your hair with conditioner, replacing shampoo step (google). I prefer Pantene beautiful lengths or curly medium/thick solutions. It's not a lie that pantene makes better conditioners than most high end brands. Comb the conditioner through while in the shower using a wide-tooth comb. Wash off.
- Squeeze water out of hair w/ towel - *squeeze*, not rub. Either put a leave-in conditioner or argan oil/cream. I prefer "one n only" argan cream. The super popular moroccain oil brand is decent but way more expensive/damages oil production after a while. Comb it through. Air dry (or leave in a hair wrap).
To straighten:
- Day *before*, make sure you condition. Your hair will be angry if you wash/straighten on the same day. Technically, the dirtier your hair, the better the outcome. Day of, slick whole head in oil (straight haired/wavy haired people, never do this). I prefer coconut hair oil for all types of hair from The Body Shop since it's cheap/a balm. I use it as heat protector (ironically). Let it absorb. Divide into three/four sections. Get a ton of clips. Heat straightener (a STEAM straightener is best, if you can get your hands on one, they're hard to find) to 390. Straighten away, using 1" *thin* sections, guiding the straightener along a fine tooth comb. Ignore steam, it's fine. Make sure you get the hair riiight at the skull, twisting the straightener at 30 degree angle as you pull it through. It'll be dead straight after 2 runs.
- After you finish your whole head, apply shine/humidity protector w/ a light hand. Use silk/satin pillowcase to maintain for more than one day.
- When you wash it out, it'll be a bit less curly at *first*. It'll go back to normal. Wash out with shampoo, use a deep conditioner treatment mask w/ a hair wrap if you have one (or just use your ordinary conditioner for 15 minutes, I don't see a difference personally). Repeat abuse.
So don't worry about damage - it'll be minimal unless you do it every single day/run the straightener through knots or something. Sexy hair is worth it.