Hi,
the overall effect is very impressive. It is a beautiful model and base. I like the trasparent lights too.
About the masking: I've made a similar work on a ZTZ-99 of HB.
I started cutting the shapes on size, put them over areas made light green by airbrush, and masked.
Then the brown, and masked it again without removing previous masks.
Then the black-green, and mask.
Then, I sprayed all the medium green background and, at the end, I removed all the masks.
Some correction was necessary, always by mask and air brush.
I've seen that it is easier to put a big piece of masking tape on a cutting plate, make long vertical and horizontal cuts to obtain a lot of assorted squares or rectangles, and then put them on the surface to mask, creating the shapes by a partial overposition of the squares.
It is less accurate in size than cutting masks to shape, but the risk of oblique contours is lower.