Flash lighting can be very harsh on the skin if not used with a diffuser like a softbox, umbrella or diffusing panel. Often times when bouncing the flash off the ceiling at 45 degree angle and the white panel retracted to bounce some of it back to the face of the subject, you will notice those specular highlights immediately. Those ugly shiny sweaty spots.
I was wondering how to get rid of those without cloning too much or softening too much of the skin. Until I came across this tip from Scott Kelby's latest book "The Digital Photography Book, Part 5: Photo Recipes".
With the use of Adobe Photoshop's regular Healing Brush Tool (not the Spot Healing Brush) enlarge the brush enough to paint over a large specular highlight with one stroke. Then go to Edit Menu - Fade Healing Brush. Reduce the Opacity to around 70% and you will see how nicely Photoshop will blend in the skin while removing the highlights.