There are many ways in which skin tone can be improved. I have posted a few tutorials earlier in this blog. This is another method and can be done in any version of photoshop. It is a non-destructive method. The original photo is not affected. It avoids the fake airbrushed look. I will be using the History Brush and Brush.
Step 1 : I have opened this free stock image. If you want to use this image, you can download it here.
Step 2 : Click the New Layer icon in the Layers palette. A new Layer 1 forms.
Step 3 : Select the History Brush Tool.
Step 4 : In the top panel change the Mode to Linear Burn.
Step 5 : Drop the Opacity down to 25% by dragging the slider at the bottom.
Step 6 : Zoom into the image.
Step 7 : To decrease the size of the History Brush press [ (left bracket). To make the brush large press ] (right bracket). Paint twice or thrice in long sweeping strokes. You will find the skin darkening as you paint more than once. Do not over do it. About twice or thrice should be enough.
Step 8 : I am now painting over the arm.
Step 9 : This is how the image looks after painting the skin with History Brush with the settings I have given.
Step 10 : Click the Add New Layer icon and a new Layer 2 forms above Layer 1.
Step 11 : Click the Eyedropper Tool. In the top panel set the Sample size to 3 by 3 Average.
Step 12 : Click with the Eyedropper on a portion of skin that is not too light or too dark.
Step 13 : Click the Brush Tool.
Step 14 : Change the Mode to Hue from the drop down.
Step 15 : Lower the Opacity to 25%.
Step 16 : Set the Hardness of the brush to 0%.
Step 17 : Begin painting with the Brush. You will need to paint once or twice. Do not overdo it.
Step 18 : I am working on the neck. See how the reddish portions go away.
The finished image. I don't think that was difficult.