So after ranting for a bit last night about slow progress and too many steps, I went out to the studio and ran a test of some new material I got from Polytek last week, got a lovely result, and all was forgiven (again).
As I outlined earlier, the small relief pieces are enormously process intensive. My hope in buying this new material was to cut out some of those processes, while simultaneously getting a better finish on the individual figures.
The problem is that the castings I've been getting out of the molds are extremely shiny, which is a function of the both the initial state of the sealed positive, the silicone release needed to get the castings out of the mold, and the nature of the urethane plastic itself. In the test last night, I painted one of my molds with Polycoat. Polycoat is a "one-part moisture-curable silicone sealant" that essentially gives surface of your urethane mold the properties of silicone, which is to say, no need for mold release, and the ability to coat the mold surface with talc to create a more matte surface.
To further flatten the finish, I also bought a bucket of Polyfil ND "...a "neutral density" filler designed for use with polyurethane liquid rubbers and plastics". The hope was that Polyfil would both dull the surface of the casting, and get more mileage out of the casting material.
So far, so good. Last night's test was a dramatic improvement over what I've been getting, and would seemingly obviate the mold-release applying, detergent washing, wire brushing, and spray painting I've done up to now. It cost me something like 150 bucks, and there's still a lot of molds to paint, but it looks like a net win. Better living through chemistry, y'all.