When Games Workshop released Cities of Death, they released a set of resin Urban Barricades and Walls. Unlike the Urban Basing Kit it is still available at the time of writing. You got six barricades and they blended in nicely with the plastic ruins which were also released with Cities of Death.
One of the key things you need to do with virtually all resin models is to give them a good wash. When the resin models are cast, the mould is given a spray (I guess) of some kind of lubricant to allow the cast model to be released from the mould easily. However the lubricant also acts as a barrier to paint, so as happened with previous models I (and others) have painted is that the paint flecks off. Washing the model in water with a drop of washing up liquid should remove the lubricant. Avoid using hot water as this could warp the resin (a useful tip if you need to warped resin back to its original shape). Once washed the model is then ready for gluing and painting, first was a black undercoat. I gave the barricades a Codex Grey drybrush, this was quite a heavy drybrush.
The next stage was to paint and drybrush certain areas. So on this model I painted the door with a green Foundation Paint and then enhanced the shell impacts with Boltgun Metal. Rust was added to metal sections using brown paint and ink.
The earth sections were drybrushed with Scorched Brown.