Ritch,
The method that offers the most control and maintains the parts best is the "X-Acto blade turned over" method. It takes some time, but is worth it. Billy's suggestion of buying a second kit is also a good one, especially since the Scout II kit is so widely available right now.
If you have some curves around the doors that the X-Acto can't do, think about using your smallest pin vise drill bits to drill holes next to each other to weaken the styrene and loosen it. Good Luck, sounds like a neat project!