Based on a previous answer: https://graphicdesign.stackexchange.com/questions/50918/things-to-consider-when-creating-realistic-highlights-and-dark-reflections-on-me
Here are some experiments. They are useful to help understand the nature of a glossy reflection and some experimenting with skin color.
Obviously, the first step is masking the skin.
Now we need to use it to create two layers. Let's call the first one Tan and simply lower the curves. I did not force them because the image you posted is low quality.
The second layer, called Highlights needs to be desaturated.
And then change the blending mode to Screen and play with the curves. Flat to the left and sudently blow them. That is what a glossy reflection does.
This is a very primitive example but can give you the basis to play with the skin tones and reflections.
An important step is to think of your concept beforehand, that way you can use oil to prepare the highlights and probably make up the model in advance.