Poker players try a lot of ways to disguise their tells. They were hoods, caps, sunglasses, surgical masks, etc. It can even be as simple as covering their mouths with their hands.
During this particular tournament, I learned that people do not pay too much attention if they can't see your face. I felt like a fly on the wall throughout the duration ofthe tournament. It was like I was observing everyone on the table and I can't be seen. It's the same feeling I get when wearing sunglasses, with an added advantage of having a clearer view.
I'd actually recommend wearing a mask except that it's hot as hell.