I use just one layer to paint these things. I use a second layer to paint new sections and then when I'm happy I merge down, then paint a new section on a new layer and merge again. I keep doing that until I'm finished, so the PSD is just the same as you see here. Its something I picked up from watching the way Ryan Church paints(I wish I could pick up more from watching the way he paints haha), doing it this way means you can use the eraser to rub out the bits you dont want, or if your not happy you can just bin that layer and start again.
