I wet my hair or CO-wash; rinse in water that graduates from luke-hot to warm to cool to seal the cuticle; spray in Ojon revitalizing mist or my homemade leave-in (of rosewater, aloe vera juice, SAA, wheat protein, honeyquat and panthenol) and seal with whatever I am using to seal with at the moment. In the winter, it is some kind of shea butter-oil combo and, in the summer, it is an oil mixture, so currently mine is avocado, coconut and olive oil. I only use a shower comb, btw.
I smooth my hair into a low twisted or braided ponytail after I have secured it with an ouchless elastic band that I have dipped in oil and I tuck the end of it under. The tension from the elastic band is not loose, but not too tight either. It is tight enough to do provide the tension needed to "straighten" the hair overnight, but not tight enough to destroy my hairline. I sleep in a silk or satin scarf and, in the morning, I make my bun and my hair lies completely flat/is completely slicked down, as it were.... I will smooth the boar bristle brush over it once or twice. I never needed gel, but last year I tried some different ones, but some of them actually defeated, rather than aided in, the primary goal.
PS: I started doing this in 2005. Before I went to this method, I could not get my hair to slick down at all. I was pressing it almost every day to get it to lie flat, which was a big no-no. Now I press or flat-iron only when I have some formal event, like once a year.