I did a shadowfax who looked pretty good, an\' I reckon the trick is blending. Every where you can see a crease in a slab of muscle, for e.g. the forelegs, paint a thin line of grey into the crease and blend it into the white very nearby. Then for the muzzle you can paint it, either, black/grey or flesh toned; both look good. Then you also have to blend this in a bit. BUT! remember that nothing really has a completely smooth transition from fur to bare skin, so add a few streaks of flesh or fur, just to show that there is a dividing line. For the fur you can do what you like, personally I think that it looks best darker than the skin to add a bit of contrast to the model. I would show you a picture but my brother covered the horse in pva glue to make him look shiny!
