For the base of the foliage I tried something different. I used green oil paint that has this transparency and creates interesting shadows. I added more in places that more grass and buses will be. I painted also on the concrete base of the container - yes I made that one out of plasticard and it still remains unpainted and un-rusted :) - that green tone of mosses and at some places on the base of the building. The concrete is a porous material and with some extra moisture you can see alot of these things growing slowly. Some dirt is done with a brown color and the road with grey oils by mixing some white with black in different proportions. The sills under the windows were made with pieces of cork and later - with the suggestion of a good friend - I filled the holes of the material with wall puty tinted with brown acrylic color.
The following photos are a bit blurry 'cause I took them with my cell phone. They show the work at the diorama after I added grass and buses, some rusty rail tracks, some old trusses and planks are scattered around and at the end of the line and an old telephone pole.
Small little piece as you can see with my hand holding it.
And my hands aren't the biggest in the world... :)