I made a small amount of progress.
I've now primed all of the parts using an automotive lacquer from Duplicolor. After the paint cured overnight, I gently sanded the surfaces with my new favorite model tool: 3M's Ultra Fine Sanding Sponge (Item 02601). To get into the tight corners, I followed-up the sanding by scrubbing the parts with a mix of water and baking soda via a toothbrush. The end result is a super smooth finish ready for paint!
I also started weathering the engines. I airbrushed a basecoat of Tamiya's Nato Black (XF-69) followed by light coats of assorted Tamiya greys (mixes of 10% paint, 40% X-22 Clear, and 50% X-20 Thinner). I also included a bit of Hull Red (XF-9) to suggest some modest rust. After sealing under a clear coat, I applied an enamel pin wash to better define the details. I'll likely do some more weathering to the engines after assembling more of the kit.
Next up: Wings.