How to smooth skin in Photoshop.

Step 1: Duplicate the background onto a new layer.

Step 2: Apply the Surface Blur filter.

Choose Filter > Blur > Surface Blur R: 5 T :15

Step 3: Add a Layer Mask.

option 1 : Layer > Vector Mask > Reveal All,
option 2 :Layer > Layer Mask > Hide All

Step 4 : Switch your color to white, select the mask and start drawing (using brush) on the skin with a soft brush. Start at the cheeks, move over to the forehead, the nose and stop on the chin. If the effect is too strong for your liking, just lover the opacity of the brush and you’re good to go!