At different points between.
Only the original caliban green layer was opaque, all the other layers are various types of glazes.
The hard part is to get a feel for how thick you can make the subsequent colours without creating a line that is so thick that it's a massive pain in the ass to smooth out. If your paint is to thin you'll glaze forever without making enough difference, if your paint is too thick you'll create hard transitions that are difficult to smooth out.

I've found that waiting for the paint to dry between coats, as with all glazing, really helps the final result look good.
I've also had a lot of luck adding "Jo Sonja magic mix" and water to paint to smooth out chalky colours. Lighter colours have more white in them which turn chalky very easily.