On this extensive Photoshop tutorial, Jesús Ramirez (from the Photoshop training channel) takes a look at replacing the skies in Photoshop in a quick but useful way.
First, you need to find an image with more or less the same perspective of the sky as the original image, otherwise the image will look strange and misplaced when combined.
There are a few ways to combine the images. The way Ramirez will demonstrate in this video uses the blend-if sliders (just click or the layer you want to combine with your main image (click on the right and in the layer style box look at the 2 bottom sliders). Choose blue (unless you have a different color skies). Now you can play with the sliders until you get the maximum blending between the layers.
Now you can add a mask and paint with black in order to deal with all those areas where the sky spill into the image. If you want to show how your layer mask look – just press alt and press on the layer mask (do it again to return to normal view).
We have looked at many ways of improving or fixing different problems with skies on previous videos including: “How to Fix a Smudgy Sky in Photoshop“, “Fixing the Sky with the Patch Tool in Photoshop“, “How to Replace a Skyline in Photoshop” and “How to Replace the Sky in Photoshop“.