Not sure what adjustments have been made to the skin. It looks fairly straight forward to me and not really painted.
Ok, I will assume that you already know how to separate subjects from their backgrounds.
Here I have a cat photo in which I used an alpha channel technique to convert to black and white. This is one of the best techniques to use in animals with fur.
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Once I had the alpha channel, I converted that into a selection.....
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.......and then the selection into a layer mask on the cat image layer.
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I then moved the cat image over to the space scene using the Move Tooll and draggig to the space scenes tab.
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I applied a layer mask to the cat image layer and used the Brush Tool to blend the edges.
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That's it! Same technique for the human subjects.
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