So I have painted up the resin bases and they have come out ok. I am not the best painter in the world but I did mean to go for a muted dirty, muddy looking base and that is pretty much what I got.
They were undercoated with cheap acryclic paint. I then did several base coats of various colours (I mainly use Vallejo paints, Game and Model color, I like their Tinny Tin colour in particular for metallics). These were then washed (I have a large tub of dipping formula sepia wash from Vallejo that I cracked open for this purpose. It seems to be pretty much the same stuff as in their dropper bottles, which I use a lot, but works out a LOT cheaper).
I tried several layers of different colour browns. I also tried different colours for drybrushing (various greys and blacks for the stone, silvers for the metal pieces and grey for the edges of the bricks).
The lighting is not brilliant but whilst dirty and muddy you can see different shades, as well as the odd spot colour (the bases have various metal gubbins embedded in the mud here and there). I am quite happy with them and I have ordered another 10 as I realised when base coating the miniatures that I have more than 20 Necromunda people in my gang box. I think I will probably paint up some of the hired guns and ratskins first before I decide on the colour scheme for my Orlocks.