For medium range to long range renders, Wetness can easily be simulated just by playing with the Specular Channel.  Add some fine grained noise into the Specular Value  - Diloma's idea of a granite node is a good one - and set the size accordingly (should be a smaller size to give a more shiny look).  

Close up renders are a completely different challenge.  I use gray scale luminance maps of drips and drops in SkinVue which adjust the luminosity of the base skin texture.  In Poser, it's a little more tricky.  You can use a Color Math node (set to bias) and blend a grayscale luminance map with a SkinTexture (see enclosed pic - warning nudity).  In Poser, there is no way that I know of to jitter or randomize the luminance overlay like you can do in Vue.  Also, Poser doesn't allow textures to be world mapped so you will see seams across different mat zones which use different UV Maps (e.g. on V4 the Body Map versus the Limbs Map)