Vanilla extract gives the acorn scent a stronger smell and smells very much the same as a white oak acorn. I have experimented with plain vanilla extract, strickly acorns only, and varied mixtures of the two both during season and off season.
The mixture is by far the best attractant and cover scent especially right when the acorns start to fall and especially later in the season when most of the trees have just about quit dropping. I usually use it more as an attractant than a cover scent.
Ive sprayed it on my boots and had deer follow it right to the base of my tree.