The layers for http://tigr3ss.deviantart.com/art/L.....uble-273420683

obviously I used layers for outlines and colour too ;p so I don't think that needs mentioning.

I DID try to thicken the line relative to the movement though, so played some with thin vs thick

Even though the shaded-by-depth and the atmospheric perspective are almost identical, they have a different threshold, where the second kicks in a bit later, after the form starts to darken it then starts to fade. You can do that by adjusting the levels of the layer mask. As a whole, it's probably much better (but more awkward) to paint on masks than to use Multiply modes and such.