For the biology people out there, question for you: does exhaling deeply immediately after inhaling something help to expel it from the lungs? For example, if one inhales smoke or other substance and then immediately exhales as deeply as they can, does that get rid of (more of) the smoke/substance in their body (than otherwise)? Or does it do nothing, or worse?

I'd approach this more from engineering, or perhaps physics.

The average set of lungs holds approx 6l and when you fully breathe out there is a residual approx 1.5l

So if you exhale a contaminant mixing inside your lungs there is only 1/4 of it left - at the same concentration so you are still consuming it the same way. Inhale non contaminated air and it has been diluted to 1/4. Note though that the whole time your lungs are consuming whatever it is.