Akina have you tried a Maxxiglide? It's a straightening tool that makes my hair really smooth and silky. I think it's great. I have fine hair but a lot of it and sometimes after it's just been dried (if I don't have time to let it dry naturally) it gets all frizzed up and drives me nuts. I put Moroccan Miracle Oil (pea sized) on my fingers. It's alcohol free and then I use the tool on my dried hair. As you can see my hair is pretty smooth!
I have very thick hair too but the turning point for me was finding a good hairdresser who cut the bulk out of my hair without removing too much length.It is now much easier to manage.I use GHD straightenning irons to get a sleeker finish.As my hair can frizz i use heavier cream based products to weight it down a bit such as rich conditionning masks,and a protective cream before and after straightenning
I have very thick, curly long hair. To feel my scalp once and a while, I get it roller set (Dominican style) at a salon. I sit under the dryer for about an hour which is really relaxing to me. Then they blow it out. It is a long process but my hair really takes to it well and it stays forever. I do touch-ups by running a hot brush through it and occasionally applying serum or coconut oil to the ends.