Three years ago I described in an article which oil I use to achieve shiny skin. But sometimes I also use simple baby oil, which is available in the drugstore for 1 €.
If you want shiny skin in the photo, the skin must be oily (or wet). So it must already be shiny in order to reflect light so that you can see highlights on the skin later. Sounds logical, right?
These highlights provide more volume in the later image. The photo looks more three-dimensional or as glamour photographers like to say: "It pops".
And in post-processing, this effect is enhanced in glamour photography with the dodge & burn method, in which highlights are lightened and shadows are darkened further. Not everyone is always up for such extensive fiddling in Photoshop, so I've created a quick Photoshop action for you that you can download here for free.
To install, click on Actions in Photoshop, then open the menu at the top right by the 4 horizontal lines and click on Load Action. Select the downloaded action from your hard drive and you are ready to go. To play, just press the small play button.
The action creates a curve layer that cuts off the highlights, meaning it pushes the light tonal values into white. This layer is then gently blended so that there are no edges. And to make sure the effect is applied only to the person in the image, a select subject mask is run (and is the reason why this action might take a few seconds on your computer to complete). This mask is usually never completely accurate, but an approximate masking is actually quite alright.