First of all, you need this stuff:
Put all your source images on different layers, and lower the opacity of the face and of the smoke source pic down to about 30%.As you can see, the first layer is called smoke. Thats actually where you will be working on, so create a new layer and put it on at the top.You will basically use the rubber stamp, getting some smoke from your source pic and putting it on your smoke layer.
Keep the smoke source pic invisible until you need it to get some more smoke. The face should be kept visible at all times, so you can place use the smoke as a template, placing the smoke where you think smoke should go, if by some chance you happened to meet a ghost with a tendency to go under burnt-out candles.I had some problems with the nose and the mouth, but here are some tips:
Wherever you think you might need it, make your brush smaller and add some touches, like making the smoke dissolve into the air, etc...Its also important that, from time to time you un-zoom a bit and take a good look from a distance. If it doesnt look real, keep on cloning! If you dont want your background to get in the way, you can always insert a completely-black background, which is shown on the picture above. Actually, I was going to leave a black background before I found the dark-room one...
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