As for the workflow.
In this case I got the main building 3D model from Ronen Bekerman freebies and first I’ve had to rebuild it to work well with UE. There were many unnecessary sculpted elements and almost all of the objects were build as one.
I am always trying to use very simple materials with basic maps - diffuse, reflect, normal. For diffuse chanel it is good to mix few textures with different scales to lose tiling effect.
As for lighting I used skylight and direct lighting together with few spot lights.