Candy: Here is a Fotheringill thread that probably covers painting windows. At least it covers it for DPM kits. Here's another on Walthers Cornerstone Buildings. I think of Walthers building as more industrial types than DPM.
The DPM N scale kits look great. The assembly is rally not an issue. The problem is that the window frames are part of the plastic casting and are one piece with the wall and lintels, etc. If you get the stone (or wood) work around the window areas done right, I will tip my hat to you. I have even gone to the extreme of airbrushing the entire structure in the mortar-stone lintel color and then coloring the brick with an Indian Red (or similar) pencil in a shading position. I am not happy with the results in a close up picture, but it is the best I can do.
I've decided to try one of the town house kits and see what I can do with it. I have to wait for my merchant's row kit so this will give me a new challenge. Thanks to you all for the great info !
I used mat board. I cut it in strips for a scale 5 feet wide and painted them a concrete color. I put in the lines with a dull pencil and cracks with a knife. I'm not too happy with it. I give myself a 5...maybe 6. I'm working on my streets trying to make them look more real. I'll post new pictures soon.