They should call them up every day and tell them to just get rid of one cigarette. Meaning, if they usually smoke 40 a day, just smoke 39 on the first day of the attempt to quit. The next day they should be encouraged to smoke only 38 then 37 the next day and so on. Then the seminar participant should call these people every day to congratulate them and encourage them to continue. I must reemphasize, this should only be done to a smoker you really despise.
You see, most smokers will agree to this approach. It sounds so easy to just smoke one less each day. Thirty-nine cigarettes to a two pack a day smoker seems like nothing. The trick is to convince the person that you are only trying to help them. For the first week or two the one downside is you have to pretend to like the person and you have to talk to them every day. They won't whine too bad either. When they are down to 30 from 40, they may start to complain a little. You really won't be having fun yet. When the payoff comes is about three weeks into the scam. Now you've got them to less than half their normal amount. They are in moderate withdrawal all the time.
A month into the approach you've got them into pretty major withdrawal. But be persistent. Call them and tell them how great they are doing and how proud you are of them. When they are in their 35th to 39th day, you have pulled off a major coup. This poor person is in peak withdrawal, suffering miserably and having absolutely nothing to show for it. They are no closer to ending withdrawal than the day you started the process. They are in chronic withdrawal, not treating him or herself to one or two a day, but actually depriving him or herself of 35 to 40 per day.
If you want to go in for the kill, when you have them down to zero, tell them don't worry if things get tough, just take a puff every once in a while. If you can get them to fall for this, taking one puff every third day, they will remain in withdrawal forever. Did I mention you really should despise this person to do this to them?
It is probably the cruelest practical joke that you could ever pull on anyone. You will undercut their chance to quit, make them suffer immeasurably and likely they will at some point throw in the towel, return to smoking, have such fear of quitting because of what they went through cutting down, that they will continue to smoke until it kills them. Like I said, you better really despise this person.
Hopefully there is no one you despise that much to do this to them. I hope nobody despises themselves enough to do this to themselves. Quitting cold turkey may be hard but quitting by this withdrawal technique is virtually impossible. If you have a choice between hard and impossible, go for hard.
You will have something to show at the end of a hard process, but nothing but misery at the end of an impossible approach. Quit cold and in 72 hours it eases up. Cut down and it will basically get progressively worse for weeks, months, or years if you let it.
I should mention, this is not a new technique. It has been around for decades. Talk to every long-term ex-smoker you know. Try to find one person who successfully used the cut down approach, gradually reducing to eventual zero over weeks or months. You will be hard pressed to find even one person who fits this bill.
One other perspective that should help you see the flaw in the approach. Look at people here who had once quit for months or years and then relapsed. One day, after such a long time period, they take a drag and are smoking again. If one puff can do this after years or decades, guess what it will do after days or hours of being smoke free. It puts the smoker back to square one. All that any ex-smoker has to do to avoid relapse or chronic withdrawal is to - NEVER TAKE ANOTHER PUFF!