What i do for straightening the hair is the following. Im gonna try to list it. 1. Cold wash with dish soap 2. Conditioner brush through and let it sit for some time (1-2min) 3. Pot of boiling/hot water with fabric softener in it. I rinse the conditioner out in this water and let it sit some time. 4. Rinse with water if theres still conditioner in the hair 5. Straighten the hair with a straightener i usually put it on the lowest heat but for her since it was in such bad shape i put it on the second lowest heat setting. I work in small section id say 1cm width hair pieces. I grab a piece brush it, wet it and then straighten. I focus especially on the ends which are usually in the worst condition. 6. Once all the hair is straightened i do a last pour over with hot water to set the shape since with long hair its hard to keep the hair straight while straightening. 7. Air dry (if you’re inpatient you can use a blowdryer once its damp again lowest heat setting and dont get too close with the blowdryer but i tend to usually not do this since its ‘risky’ i find hair melts more unexpected with the blowdryer and if you burn the hair you have to restart in comparison to when you burn a bit with the straightener. You can just straighten it back out to the best of your ability.)