[Reaper Pathfinder] GGS painting contest- WIP on base 2

Yesterday, I've proceed with the base for Valeros.
First, I've added some elements to fill the space and make the environment more interesting.
The small flocking between the slabs has been fixed with a mix of PVA glue and water. Actually, I haven't pigment to create the dust so I use this kind of flocking instead.
In this phase I've also placed the mini to have a clear overview.
As Valeros is tintled toward the right of viewer, I've placed a piece of wood on the opposite direction to create a triangle. It's a tip I've learned from the diorama makers, the triangle lead the viewer toward the focus point of the scene which is Valeros'face.


Now, my idea for the scene was to use the front of the base to place the shadows of the foes. Because I want to create the idea of the ambush but I cannot place other minis due to the rules of the contest.

So I've made an experiment: as I always use pre-shading techniques for the priming of my bases, I though It could be a good idea to integrate directly this shadows during this step.
I've created a mask representing the foes and place it in front of Valeros.



Then I proceed with the priming of the base following the pre shading techniques:

_ first step, I spray the base in black without the miniature and without the mask to be sure that all the areas are fully primed.
_ second step, I place the miniature and the mask and now use the white colorspray to place the lights. I spray the white only in one direction directly in front of the base. My intent is to place naturally the shadows thanks to the mask and the mini which should let the area behind in black. 
Here the result.

It doesn't work. Actually I have a zone of shades in the front of the base and also on the wall behind Valeros but I didn't succeed to create a clear definition of the shadows.  I think it's due to the distance I spray the white, too far away from the mask to create the effect. I suppose It's the kind of job I should do at short distance with an airbrush.

Ok, it was an experiment, not a big deal because anyway I'm happy with the general lightning of the scene.  I will define the shadows with my brush during the painting process.
Ok, I think I've done with the building of the base. Now it's time to play with the colors.