This is a very usefull, easy and professional effect for any idea you have in mind without the need to blend smoke photos to the design. And with the possibility to use the effect on all the canvas without fear of bad resolution.
Erase the area where you want the smoke.
Go to the smudge tool and pick a relative medium to big size with no hardness and apply a streng between 40 and 60.
Now reduce the size of the area and raise the strenght 10%
Make circular shapes clockwise and counter clockwise over,trying to bring inside some white and the idea of air flow.
Repeat the step 6 until you get enough vanishing then make new shape layers, rasterize and apply the effect in the same order to make lights and shadows.
2.5 mb .zip [ai, eps, svg]