I was a heavy smoker and tried nicotine gum. Although it helped somewhat as far as providing the addictive nicotine, a lot of smoking is psychological, and it gives you something to do with your hands. The gum didn't work for me.
I would recommend that he have his GP prescribe him Zyban. Within days, he won't be able to stand the taste of cigarettes, and every time he tries to smoke one, will put it out immediately. At least that was my experience. I have to admit that I slipped from never smoking at all to just smoking if I have a drink, but even then, I don't smoke the whole cig, and I never even think of them otherwise. Have him try Zyban. I guarantee it.