I found a tutorial on a technique used for portrait retouching that is very good at retaining detail while retouching skin.  Frequency separation, is when you retouch an image on two layers. One that preserves detail and one that is just tone and color. So that when combined the two layers produce the corrected retouched …

http://www.varis.com/video-tutorials/ The tutorials on this site are really great. The author is teaching us how to generate the very best image quality by using all the technological abilities of digital processing. Well worth the look.