When it's bitterly cold, I wear a full-face type camo stocking cap that I have cut my own mouth opening into.
I can only wear it when it's REALLY cold, though, because otherwise my glasses fog up.
In normal temps, I just use a homemade 1/2 mask that I made from a piece of old tan colored t-shirt. It's sewn on to a piece of 1/4" elastic for a headband. I again, just cut out my own mouth opening. The mask covers from ear to ear & hangs down long enough to slip inside my shirt collar.
In early Fall, when it's still quite warm, I just use camo face paint where I don't have any beard...& under my eyes/behind glass lens {to cut down on possible reflection to critter, which may/may not work}.