When your hair texturizer starts to go grey the melanocytes slow down there productions of melanin. Melanin produces the color and so the hair turns grey. Another thing that happens to hair is it gains cuticle layers. So from what I remember the average persons hair not grey has around 12, when it goes grey it goes to 27 layers of cuticle, this in turn makes the hair more coarse.
The main categories of hair texturizer are kinky, curly, straight, wiry, wavy. From that you can add density: thick, thin, medium. From there you can add hemispheres of our heads. Hair strands can be majorly different from one section of hair to the other.
His hair texturizer is short on the sides and back but lengthier on the top. It probably took from one haircut to the next, however long that is for you, to get the top as long as it was there.
Relaxers are most commonly used by people with kinky hair texturizer. Popular among African-Americans, relaxers are thick and creamy and very strong. They will make your hair stick straight if you want. However, the chemical content is high, and it too can be damaging if left on too long. If it gets on your scalp it will burn it leaving blisters and scabs. It should only be done by a professional. When your roots grow out they will be curly and the rest of your hair will be straight, so it will require touch-ups regularly.
His hair is very likely naturally thick like that and it wouldn’t take one long to get such a look of they had that type of hair texturizer. I have that type of hair. A comb with large, widely spaced teeth would do it.