I covered the bases of the 3rd section models (where I ran out of bases at the beginning) with filler and placed again some small rocks. To hold them in place and not loose them again, I mixed some PVA into the filler.
When that was dry, I covered all bases in PVA and sprinkled on sand.
When that coat was dry in turn, I sealed the sand in with a mix of PVA, water, black acrylic paint and washing liquid (to break the surface tension and help the mix to flow into all the nooks and crannies).
I have not decided yet how to do the bases for this project, so for the time being, these models are done. After the foto shooting, they got a coat of gloss varnish to protect them from any harm.
Next up are the senior leaders, anti-tank rifle team and light mortar team.