Well the higher the gloss the wetter it will look. This is done using "Specular_Colour" and "Specular Value". The lighter the colour and the smaller the value the more glossy or wet it will look. Try a light grey for the colour and a value of 0.2 or 0.1. it is a good place to start. You can try playing from that point and see what you like more. You can go to white and 0.1 for the highest gloss.