Initial modeling is kept very simple. If the model is provided by the client I will simplify to show essential information (particularly revit models). i prefer being sent a pdf with plan and elevation information along with CAD info.
I will generally execute an initial series of renders where I play with lighting. textures are kept simple and are generally just basic shaders. The initial render works as an underpainting.
using a wacom cintiq I then draw over the top of the render/underpainting in photoshop and begin to paint in the the values, textures, and entourage. context for this image was gathered using google earth
initial model
initial render/underpainting
final painting
initial model
initial render/underpainting
final painting