I have done this, and furthermore I have done it so that the character can look progressively more sweaty. I was going to make a tutorial on this but I never got round to it. So here is the bare bones. First, let someone else do the hard work. Purchase one of the "wet" skin textures available, like Miss April here or Beach Baby at RDNA. Now, if you want to use that skin texture, you're done. But most likely you want another character to look wet, so you need some way of transferring the droplets from one texture to another. This is quite possible. Load the wet texture into Photoshop or PSP. Desaturate. Now play around with brightness and contrast etc until the water drops stand out in white/grey and everything else is black. Save to a new file. Load the skin texture you want to use. Paste in the droplet image as a new layer. Set the layer mode to Screen, and the white will come through but not the black. Adjust the opacity of the layer to get a heavier/lighter amount of moisture. Save your new "wet" texture as a jpg and use in Poser.