As long as he wants to quit smoking, he's already halfway there. There is absolutely a lasting positive effect from using psychedelics to change habitual behaviors, but at the same time it's all in your head like a placebo. As long as he wants it to work and believes he can quit, the actual method isn't that important. Just be careful with it being his first time.

I heard about someone who tried to quit smoking by dropping acid and licking the inside of an empty ashtray anytime they wanted a cigarette, supposedly they haven't smoked since. Smoking really is disgusting and off-putting to all of your senses, you just get so used to it you don't notice it anymore.