There are a few raised elements on the shield so I cut those out of scraps. I did it free-hand and it took me a few tries to get shapes I was totally happy with, but since they all had beveled edges this was probably the most efficient approach. If I had thought of it, I totally would have tracked down that 45 degree matt cutter I have somewhere for matt board. Instead I went for the trial and error approach. Meh.
Once the edges and raised elements were glued down, I went over everything with paintable caulking and created smooth, rounded transitions. It took 2-3 coats with sanding in between for me to be happy with the texture because I was really hoping to put a metallic finish on this thing.