By the way, the Intrude tool in Wings is awesome for doing interiors. Give it a try; select a face, right click, and choose Intrude on the menu.
Actually, the fastest way to see quickly how Intrude works is with a sphere. First create a sphere. Switch to face mode and click on a bunch of faces to select them; don't select polygons that are adjacent, but rather space them out. Now right click and select Intrude. Move the mouse to change the thickness of the Intrude operation, and click to finish. Hit Space to deselect everything and now tumble the view around to get a good look at what happened. Automagic interior!
Actually, the fastest way to see quickly how Intrude works is with a sphere. First create a sphere. Switch to face mode and click on a bunch of faces to select them; don't select polygons that are adjacent, but rather space them out. Now right click and select Intrude. Move the mouse to change the thickness of the Intrude operation, and click to finish. Hit Space to deselect everything and now tumble the view around to get a good look at what happened. Automagic interior!