I use paint, a face mask, or just my beard. It depends on my mood. I never get crazy with the paint though. I have one of those 3 color sticks that look like small deodarant. I just hit the high spots to try and flatten my features.
I will state I used to just smear a ton on for no other reason than wanting to look like rambo or something...now it's precise lines usually darker to hopefully simulate branches and "possibly" break up the face's outline.
Face paint for hunting has been around since the 80s... May have become more popular with the duck commander crew blowing up, but they by no means started it.