just out of curiosity...how come it wasnt shot lit with smoke?
you could probably take a closeup shot of the end of a lit cigar, and get it in there....just make sure the angle is the same.
smoke will be a bit tougher....i would probably shoot some smoke on a black banckground, and put it on top and mess with blending modes and opacity...
of course the easiest solution....if you have access to that dude again...reshoot lit.
i wouldnt do it by trying to draw the stuff in...it will likely look unreal.
i would be interested to see your results! please repost when done.