If you ever experienced difficulties with importing and exporting files between ZBrush, Maya and 3DS Max, you would be interested to know about Styx - the script package that makes faster importing-exporting files between the programs.
Now the most difficult is to create chaos. In real life, for example, you do not find absolutely clean surfaces in architecture - there are water stains on walls, dust, dirt on the borders of asphalt roads and so on.
Every project I start with collecting information: drawings, textures, photos etc. Professional architecture photos help to understand the atmosphere - to play with light and shadow and to create realistic details of the environment.