Thanks folks

What did you use for a base before the wash?
The kits are from Oshiro Model Terrain, who sprayed the brick sections for me using a matte brick red.
I then painted over that using a Yellow Ochre acrylic (by System 3, I think) from the local art shop, with various dilutions and additional coats which affected how much of the red showed through from underneath. It’ll change colour though, as I add more dry brushing and washing.