Choose a photo you would like to retouch. I picked this photo of: Adriana Lima with no makeup on. Its not a bad photo, but lets see if we can give it a boost!

Pick the smudge brush and lightly go over her skin.
Opacity of brush: should be anything under 12% or it will start to blur and look really bad.

I lightly when over her skin making it more flawless

Use your color picker tool and pick a color off her face. Then make a new layer. start to air brush her face. go around her eyes, eyebrows, and lips.

Play with the layer settings. Here i picked color and lowered the layer opacity to 23%

Finished. I stopped at Step 4 because the photo didn't need anything else. You can add lip stick, eye shadow, etc if you want.