The specular ior and roughness define the glossines of a material.
It will be more visible if you use a bump or normal map due to the different directions the light will bounce.
Most realistic result would be to set IRO to 1.33, set roughness very low and increase specular value.
RedSpec has made a series of human skins and wet skins you can apply to your own characters. http://redspec-sss.com/shop_skin.html
It gives quite good results. If you are using Poser and M4/V4 get the M4F ones for Poser.
Configuration: Windows 10 64bit Creators Edition, I7 6850K, 128GB, 2 GeForce 1080ti, P11 Pro SR6