Create an inside bufffer in ArcGIS and retain attributes from the parent feature class. This enables things like using the same symbology definitions for both the outline and buffer when using stacked layers with transparencies.
Requires Arcinfo.
Use the Buffer Tool from the Analysis toolbox and enter a negative value for the buffer distance. Pick OUTSIDE_ONLY for the side type and then dissolve on the relevant attributes.
That's all you need to know (though there's more if you want it). Results saved in T:\Cartographics.gdb for unit sharing.