I've no experience of creating skin tones other than 'painting' skin around eyes (painter+wacom) but I think I'd be tempted to set up alpha channels for the different bits of the body in p/shop to make reselection easier - it'd also help if you wanted to modify same. As regards the tones themselves, maybe create (on another layer) some clouds using flesh colours that aren't too different from each other and add noise where appropriate. Using selections derived from the channels you should be able to steal suitable chunks of 'cloud' for the bits being worked on. The blur/median/motion blur/finger paint and noise(again!) filters also spring to mind here. If the above pieces were montaged to create a basic background colour for the body it might give you something to work on and improve, rather than trying to get it right first try on a blank canvas. You might also try copying this layer and play around with the blending modes? Modified versions of the original channels would give you access to making selections for shadows/hilights/image manipulation in a controlled manner until you've had a bit more practice - after all the subject matter you've chosen is very difficult! I also suspect painter to be the better choice of s/w Sorry I can't offer specific tips - if I could, my scratchings would be hanging in the Tate or similar.