Good progress with the bases. In the last pic you could see some finer rubbles I added, railroad modelling gravel I bought probably 20+ years ago and that I have finally used for something. I then sprayed the bases with Zandri Dust, touched them up manually with more Zandri Dust and added a few details in Retributor gold. I then proceeded with a heavy drybrush of Ushabti Bone, picked up the details I messed again with Retributor Gold, and added some Warplock Bronze and Leadbelcher on more details (most notably the half door and broken pipes respectively).
The Zandri Dust spray melted part of the stairs I had carved in polystyrene, my attempt at covering them with some paint before spraying proving inefficient. Hence I added some textured plasticard to reduce the impact. As the buildings are quite destroyed, this is not too much of a problem but definitely something I need to keep in mind before spraying other things incorporating polystyrene.
Picture of the base with Abaddon Black covering the stairs
Same base after spraying with Zandri Dust, notice the melted polystyrene and the added textured plasticard.
Close-up of the details I picked up with Retributor Armour and Warplock Bronze
I then proceeded to drown them with a copious amount of Agrax Earthshade.