I think what I do would be considered using it as a leave-in. I use coconut oil to detangle and braid up/twist my hair to go under my wig.
Basically, on wet hair I section, add a gob of coconut oil, comb through, braid/twist. For the rest of the week I just dampen with water and add castor oil to my ends.
So yes, I leave it in. And I use alot. I saturate the sections with coconut oil. It absorbs by the next morning and my hair turns out very soft and doesn't feel oily.