When I first read this I assumed it was because the sun's glare was degrading your ability to observe. Now my understanding is you're wanting to degrade others ability to observe you. However my advice stays the same, if you were in harms way maybe not.
I have used ARDs, panty hose, cat-eyes slits, "bird nests", you name it for years so I will caution you- any of these will degrade the optical performance of your binos/spotter/rifle scope. If you are going to spend your hard earned money and buy the best equipment you can afford, why degrade it with such trinkets? Best thing is to tuck into the shadows if possible (as stated), if shadow isn't available make you one.