Basic framework is 1x4's supporting the standard plywood and homosote base. This method makes it easy to change elevations of the surrounding topography rather than living with miles of plywood prairie. The New England flavor of this scene is unmistakeable. If you have seen my clinic you know that oatmeal scenery is a combination of Celluclay and Perma-Scene. In my opinion anyone still working with hydrocal plaster has been inhaling plaster dust for too long.
Structures are a combination of kits, kit-bashes and scratchbuilt.
Where possible, I use commercial parts and buildings to save time. However I recently made the discovery that in many cases scratchbuilt structures can take a lot less time and provide more enjoyment than some of the craftsman kits now on the market. The one exception is the Delabarre Tool and Die Factory. Kits produced by this company can be built by the average modeler and will provide hours of enjoyment. In summation, I have found that it is easier to model a prototype of a particular era, as it helps provide necessary constraints.