I have 4a/b thick and dense almost APL hair who wears my hair straight 100% of the time. I have managed to transition and rock my fully natural hair straight with minimal reversion with the following steps:
1. Shampoo - Quidad Cleansing Oil
2. Condition - Joico Intense Hydrator and Joico K-Pak
3. Leave Ins - Aphogee Keratin Mist, Giovanni Direct Leave in, Morrocanoil treatment, Argan oil
4. Blow dry & Flat iron
5. Wrap hair at night and secure with satin scarf.
I live in Texas with 70%-80% humidity and I make it work