Method 3 - Using an Overlay Layer

I'm again going to quote Amy's post. I like this method esepcially because it's only a single layer and very easy to change the effect.

"make a new layer, fill with 50% grey and set that layer to "overlay" and paint black or white (again, 0% hardness on the brush, 100% opacity, 1% flow) to carve down or up. This method sometimes adds more saturation to the carved shadows than i would prefer "

Step 1 - Create the Overlay layer

Create a brand new layer above your photo, and fill it with 50% grey. Click Edit>Fill... (or press SHIFT-F5) and select 50% grey from the 'Use' dropdown

You now need to change the blending mode to Overlay.

Fig 13.

Step 2 -Paint in your highlights and shadows

Using a soft, slow flowing white brush paint in highlights, and the same brush but black will increase shadows. Easy huh!

Here's another roll-over.

Fig 14.