My friends, I painted the sandbags and the terrain. Let me tell you, my suspicion was correct: sandbags are really hard to paint and post-shade! Even if you use the pre-shading and glazing method, they're not easy because they're just so flat... Maybe that's the only correct approach to them - embrace the flatness and let them look like that!
The terrain was definitely more enjoyable. It was great to see how it transformed the base and made the greyish weathered wood look just right! I started by spraying it with Flat Earth and then I post-shaded the raised sections a little by adding Dark Yellow into the mixture. I left the bottom of the trench darker on purpose, as this is where moisture collected all the time.
Enamel washes enriched the surface, and this was carried out with Kursk Earth as the primary color, and Dark Mud with some Track Wash for the darker tones and shadows. Clumps of earth and stones were then picked out with acrylics, and I paid special attention to the orange tones visible in the movie 1917. A quick dry-brush with Rainmarks Effects knocked some of that artificial, painted look down.
I still have to mess around with some of the textures - the sandbags definitely need a quick blast of VMS flat varnish because the enamel paints and thinners left some satin tide marks on them. The bottom of the trench would look great if it were wet, possibly with some muddy puddles... well, I'll see what can be done!
Right now I need to finish correcting those errors, and paint the remaining details - tarps, shoe, flimsies, entrenching tools, and add electric wires to the telegraph pole and on the wall!