Question: is it essential to use shrink wrap for the "shoot and see"? I wonder if using black plastic over a light background might work and eliminate some steps. Particularly if one was to make a frame, the edges of which were a bit narrower than the cardboard backing, so that the cardboard was curved thereby stretching the black plastic and inserted in the frame. You could get the thinnest mil black plasticcheap, eliminate a paint step, and reuse the frame.

This needs more study...................