Yes. Ceramic is best. In a lot of different things, actually. Not just for straighteners. But the best straighteners are ceramic. Also ceramic knives are fantastic for... stuff.

And also yes, the oil can make your hair super greasy looking. It may take a couple times of times to find the right amount, which obviously will depend on how much hairs you have.

As for sectioning and layering, I'm not the best at that. so. ask actually girls that one.