This is where I started. The original image.
First I used the Content Aware fill to clear the area. It's more funny than useful.
The first quick painting job. I roughly put up some skin tones and brought back the mouth. Basically I used the brush tool and the color-picker while brushing. If the brush tool [b] is active You just simply have to push the [Alt (Option)] key to use the color-picker. While manipulating a face it is allays useful to have a basic knowledge about how to draw a portrait.
I made things smoother. I used the brush [b] and the smudge tools [r]. If You don't have a wacom pad this phase can be really painful. It might help to use selections at places like the chin where you want sharp edges.
I also used the burn/dodge [o] tool to add some shadows, lights and details. I used this tool set to the midtones range at a very low precent (2-5%) painting several times over an area. The easy way to toggle between burn and dodge is to hold the [Alt (Option)] key while using one of them.
After this I added some more lights and shadows on the entire face with a layer in overlay mode. What overlay does: If the layer is 50% gray (#808080) the layer below won't change at all. If it is lighter the layer below gets lighter if it is darker the layer below gets darker. It's a great way to add lights, shadows and contrast to a picture.
I select an area of the forehead. I will use this for texturing the chin. First I copy it to a new layer [Ctrl (Command) + j]. Then I turn it into grayscale [Ctrl (Command) + Shift + u]. Then I press [Ctrl (Command) +m] to get the curves and I make the layer less contrasty by leaving the midtones, lowering the highlights and lightening the shadows.
I change the layer mode to overlay and use the puppet warp to make the lines of the surface follow the structure of the face.
I use the previous technique several times until the whole lower area of the face is textured.
I use layer masks to make the little surface pieces mix smoothly into the picture.
Finalizing the image.
What I like to do is to make a copy of the whole image onto a new layer by pressing
[Ctrl (Command) + Alt (Option) + Shift + e]
Then I use some modifier/effect/retouching then change the layer opacity to fine tune it.
Then I start over again with copying to a new layer.
What I did with the cowboy:
Adding some lights+shadow to give it more depth and shape.
Bringing back some of the neck part of the original image.
Retouching / fine tuning the mouth area.
Using a smart object with HDR toning to enhance some details.
Using the same in overlay mode to enhance overall details, make the picture more unified.
Using some vignetting at the edges.
Putting some blueish color over the shaved area.
Putting some shadow on the neck.
Using shadows/highlights to make the whole thing more graphical by lightening the dark areas on the hat and clothes.
The final image.