This is one of my various techniques that I use to create a quick sketch. 45min. total.
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I used different photos to collage a base for the painting using different layer options
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I used lighten layer with a mask to get some city lights
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started painting over and picking up some building details
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created silhouettes with layer masking for the flying objects
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Used overlays and color dodges to enhance the focal point and push the light and darks.