It's always very handy to use a Smoke Atmosphere for some of your video scenes... Use "overlay" or "screen" mode within video editing/post-production software to add as an element in your video. Here are a list of free smoke video to download so you can use them in your production... Enjoy !
27 smoke effect by digital meals http://digitalmeals.blogspot.fr/2012/03/smoke-atmosphere.html
Smoke by Ro Tierney:
Another one by Peter Norby
It's a good start point :) Now let's work !