Finally got all the mortar in place. Developed another new approach on Friday that sped up the process a bit. I'm using the flexible rubber edge of a contour sanding tool. It's rubber and worked as a squeegee to spread the joint compound without damaging the paint below. The razor blade occasionally scraped to deep and removed some brick red paint.
So here's the mortared building, although you can only see two sides. Take my word for it, the other two sides are done also. I will probably seal all this before applying the aging solution.
Lastly, I am now the owner of another 3D printer; an Elegoo Mars 3. It's got 30% more build volume, 4X faster exposure, and a 4K monochrome LCD with 8 times the X-Y resolution, than my "old" Elegoo Mars 1 (Classic). It's already going to produce great parts for the turret project. For example: I can print the entire officer's compartment floor with the rammer machines attached in one piece. My old machine wouldn't fit it. And it will print this in five hours instead of twenty. I'm keeping the old for non-critical jobs or thin ones that will print quickly.
The new machine is much more refined than the first generation. Elegoo has come a long way in less than 3 years. They've sold a lot of printers and got a lot of feedback which they incorporated.