I have started work again on the walls of Dura Europos. At the moment, I'm slowly adding texture, using textured masonry paint from B&Q. It's slow work, because I need to add it to one face of each model at a time and wait for it to dry before doing another face. It's a matter of painting it on fairly generously, and then stippling all over to remove the brush-strokes.
I'm quite looking forward to having it all done - I hope it's going to look good. I just need to not rush it, and to be patient with the painting and dry-brushing.