Either simply buy a specialized "beauty" plug-in (GenArts Sapphire Beauty, Digital Anarchy Beauty Box, Boris Continuum, Magic Bullet Cosmo) or learn to mangle channels using suitable effects. E.g. you could convert your image to a HSL representation using Channel Combiner, apply a Levels effect to define your "selection" parameters similar to PS' Color Range, then convert it back to RGB with another Channel Combiner and then use the result as a Matte on whatever blur effect on a duplicate layer you fancy to smooth your skin/ create a soft glow...
Depending on your shot you can also use some procedural matting to isolate skin on a separate layer. Colorista has the ability to key skin and only apply color correction and pop to the skin.
Compositing is all about learning to separate elements in the scene. A good understanding of the use of color or luminance channels to generate procedural mattes is critical to your success.
If a procedural matte cannot be created then you'll need to do some roto work. A procedural matte is a matte created by manipulating pixel values through a procedure, roto is a matte created by drawing on a scene with a mask or brush.
Here's a screenshot that shows how color range key and a little box blur was used to create a track matte to reveal only the skin tones from a copy of the footage that was then blurred and screened over the original footage to create a brighter and glowing skin tone for my daughter. The instruments and the clothing are not effected so they remain sharp and at their normal tones. Curves were applied to the whole scene with an adjustment layer to give the final look. This is just one of hundreds of ways to pull a procedural matte to isolate areas in a scene so they can be modified.