you can use the parametric mask to isolate the skin tones then invert the mask to pass them through the lut module. You can also use the parametric mask to select shadows or highlights.
probably not going to produce a nice result though, you’d be better off finding a lut that handles the skin tones to your liking. For what its worth the main reason I like the lut module is because it can compress skin tone hues in a pleasing way.