Frequency separation allows you to retouch texture and tone/colour independently for powerful portrait retouching.
Although the term frequency separation is initially intimidating, the concept is straightforward. By automatically separating your image colour/tone and texture into separate low and high frequency layers, respectively, you'll be able to retouch colour/tone and texture independently.
Skin tone and colour (shadows, blotches, etc.) are made smoother by blurring with the Dodge or Blur Brush Tool. The Healing Brush Tool also works well here.
Unwanted textures (spots, stray hair, blemishes, dimples, and wrinkles) can be removed with the Clone Brush Tool or Blemish Removal Tool.
To apply frequency separation:
From the Filters menu, select Frequency Separation.
Drag on either high or low pass preview panes, to set the Radius (or use the slider in the dialog); this sets the balance between texture and tone. Set the value so the image's Low Frequency preview blends image colour and tone but without losing major features within it.
(Optional) From the dialog, check Feature Protection Tolerance and set a tolerance value on the slider. This preserves major facial features when applying subsequent brush strokes.
To retouch colour or tone:
From the Layers panel, select the Low Frequency layer.
Apply retouch tools to the layer as appropriate.
To retouch textures:
From the Layers panel, select the High Frequency layer.