Of the 55 filters in Color Efex Pro 4, one of the most versatile is “Glamour Glow.” This filter creates a softening effect with a mild glow that is most often used in portraits. However, I’ve found it to be a perfect choice for smoothing out skies in HDR images and landscapes. To get this effect, you’ll want to add the Glamour Glow filter in Color Efex Pro 4 and dial up the saturation slider a bit. Then, use Control Points to restrict the effect to just the sky. You may need to use a combination of plus (+) and minus (-) Control Points to get the look just right.
Here’s a video tutorial of how I use Glamour Glow on HDR/Landscape images: