Starting with this:
I made a more refined template:
And then I started gluing & cutting:
After a LOT of putty work, sanding, and a @#%$^load of krazyglue, the matte board & bits essentially became solid plastic:
A quick spray of black, and there's a better sense of the whole, so far:
The other thing the basecoat did was really emphasize the areas still in need of further sanding & polishing... so, not quite ready for paint. Still, not bad for under $5.
For anyone interested in the techniques I used, look
here for a much better version.