Here's my first attempt at skin smoothing. We seem to each have our own way of doing the same thing.
1. Duplicate the original layer.
2. Use the wand tool to select the larger areas of skin, don't worry about getting stuff you don't want. De-select contiguous, and click the Add to selection. Change the Tolerance to smaller numbers, I usually stop around 15.
3. Using the paint brush and eraser tool set to Normal, 100% and 100%, toggle between "marching ants" selection and quick mask. Paint to add to the mask, erase to remove the mask. Red is UN-MASKED. Start with a large radius and work your way down. Toggle between Quick and Standard modes using Q to make sure you have everything.
4. When you have all the skin you want smoothed, switch to Standard mode and Save your selection.
5. Feather the selection. The amount depends on the size of your image.
6. Apply your preferred smoothing method.
7. At this point, you might see you feathered too much or too little. If so, you can step back, reload the selection and modify you mask selection or change the amount of feather.
Filter settings used here:
On Bottom Layer:
Unsharp Mask: Amount 150%
Radius: 0.9
Threshold: 1
On Top Layer:
Gaussian Blur: Radius 1.3
Layer Blend: Normal
Opacity 75%
Before:
After:
Cheers!
Glenn