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Step 1 Open up an image of someone with his/her hand in the position so you could make lightning flow out of the vingertips;

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Step 2 Then open a new document with the size 500x200 and add the standard gradient to it;

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Step 3 Go to Filter>Render>Difference Clouds;

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Step 4 Press CTRL+I to invert the image;

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Step 5 Press CTRL+L and drag the middle arrow ALL THE WAY to the right;

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Step 6 Repeat step 2, 3, 4 and 5 two or three times, depending on the amount of visible fingers and place them inside the image;

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Step 7 Change the blending-mode to Screen;

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Step 8 Resize them and position them in the right way;

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Step 9 Use the Eraser to erase the corners and borders;

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Step 10 Press CTRL+U and change the color to a blue with a purple haze;

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Step 11 For a more professional result, grab the Brush and start brushing some blue ON the person and press CTRL+L on the lightning layer to make the bolts even sharper.
Good Luck!
