That protein treatment is very popular, I hear mostly good reviews. I'd say try it. And like you said, it's cheap.
Oils that DO NOT penetrate the hair (but are therefore good for 'sealing hair'):
- Sweet almond
- Evening primrose
Oils that DO penetrate the hair:
- Sunflower Seed
- Meadowfoam seed
- Shea butter
And I believe aloe vera gel is in between.
Also, like NvmbrCurlss said, dew points also played a BIG role for me. The humidity here is so high even in winter, I'm banning humectants in my leave in and styling products.
And of course, density and length decide how much I use of everything.