You're not supposed to smoke on the MC, but I did during sporadically during my first two MC's and once during my third. On my third MC, I didn't smoke until near the end, and then I only smoked two cigarettes, but I felt so sick the next day that I swore off smoking forever --one day at a time. I haven't had a cigarette in about six weeks and I feel great. Whenever I get the urge I think about how sick I felt after smoking and the urge goes away.
Anyway, my point is that it's better not to smoke on the MC, but you can still do the Master-Cleanse
and smoke - you just won't be getting the maximum benefit that you would if you didn't smoke. I still believe it is worth doing, but some disagree and think you should quit entirely while on the MC.
Good luck to you!