I believe it all works to an extent but if you dont play the wind right more often than not they are going to bust you. Playing the wind remains to be my best defense against a whitetail's keen sense of smell.

IDK HOW ANYBODY COULDNT BE A BEIEVER. I WAS STALKING A BIG 8POINT THAT TURNED OUT TO BE MY FIRST BUCK AND BEFORE I STOOD UP AND STALKED I PUT ON ALOT OF SCENTKILLER. I GOT UP ON THE SIDE OF A HOLLOW AND LOOKED FOR THE BUCK. A DOE THOUGHT SHE SAW ME SO SHE WOULD LIFT HER NOSE AND TRY TO SMELL ME BUT COULDNT DO IT SO SHE KEPT EATING. I KNEW I SAW THE BUCK GO NEAR THE DOE SO I JUST WATCHED AND HERE HE CAME...HE TRYED TO SCENT ME TOO BUT AS SOON AS HE WAS DONE AND GO BACK TO EATING...BANG!!!! NOW I ALWAYS HAVE SCENTKILLER ON WHEN I GO IN THE WOODS.

It's important to note that the doe was downwind of us the entire time as well.

jay and BigWoodsHunter57 say it very well. Your not going to out wit the nose of a mature animal very often. Any scent that is out of place will sent a mature buck or doe to parts unknown. Playing the wind is the #1 way to shoot deer. Learning about how wind and breeze works is essential to long term success. You simply don't have to rely on expensive products to harvest whitetails, you only have to learn you craft. I have always been of the opinion that the nose of a deer is the toughest part of their defenses to overcome.

I think both sides of the issue are important.
Yes playing the wind is critical but where I hunt it is fairly densly wooded so because of the trees the wind seems to change directions quite often, so I beleve that in this kind of situation the scent control can make or break wether you get a deer or not.

I still hunt the wind because, I do sweat and even though I use scent free products to wash head to toe. It is better to be same than sorry. But while wearing scent controled clothing and hunting on the ground I had a deer literally walk within inches of my feet before first light. I was concerned I was going to get stepped on and what would happen next.

I absolutely believe in endura-skin from bass pro. All I do is spot and stalk and last year I had does passing me close enough for me to knife. (or ride, which given the option I'd chose the latter)

It definetly does work. However, I feel that some people trust new technology too much and dont study the ways that people have been killing deer for hundreds of years. There was no scent control back then, and no deodorant. Use scent eliminating clothing but still be aware of the wind direction. Mature bucks dont have to smell human odor to be spooked, all they need is a smell that is out of place from the normal surrounding woods and they are gone...

Try doing it without scent control ... have your friend cover his face this time.