I found an excellent skin airbrushing tutorial over at tutorialpulse.com. This is a detailed thirteen step tutorial which layouts exactly how to have smooth skin using Photoshop. Each step contains a detailed description as well as a high resolution image to explain the procedures. The full article can be found here.
There is also an option to download the source files for free. If you want more digital makeovers checkout the, Digital makeover series and remember to subscribe.