I did this a long time before I started reading lesswrong, the idea of doing it as an organized, self experimentation type thing didn't even occur to me.

This was about five years ago so I can't offer you much detail. I quit flat out, cold turkey. I think the gagging thing was most helpful in the initial two weeks when intense cravings where a problem particularly at parties etc. where people were smoking around me. I remembered to induce gagging I would guess about 1/3 to 1/2 of the time I consciously experienced a craving, which would have been dozens of times per day for the first week and far less over time. I did it whenever i caught myself thinking in any real detail about cigarettes, the taste, etc etc. One of my main reasons for quitting was were the queasy feelings upon waking - I'd remind myself of those general disgusted feelings, recalling as vividly as possible the unpleasant feeling upon waking up etc.

I have no idea which of the various things i did contributed to my success. I suspect developing the habit of physical exercise has been a big help because I find it impossible to run, swim or box if I have smoked in even the last week. I did relapse for a few months about two years later.

Instant uncontrollable vomiting definitely wasn't a problem. I have a fairly low gag reflex, so I could gag a little to the point where I felt a slight response in my eyes and stomach muscles without worrying about actually vomiting, although for all I know this might increase the effectiveness of the technique.

My biggest caveat is that I had been truly addicted for at most a year and a half. It might not work so well for someone who's been on the death sticks for decades. Particularly if it's been entrenched into their routines.