If this is a still you can bracket anyway. I've found that to 'sell it' with smoke you need easily 2 or 3 times as much smoke density as your eye thinks, and maybe more. I've used 5 or 6 cigarettes mashed together out of frame just to represent one. For about 3 or 4 setups, I bought a pound of incense. It's just that thin line between realism and overdoing it.
Smoke is translucent.
Incident light readings work fine for solid objects. Presumably Jay's shot is in color, so the cigarette smoke would be blueish. Also, smoke is going to be a various densities at the same time. Which is why I say it's as much a light it by eye as a light it by spot meter.