Some mappers say to overlap the area brush, but I don't and it works fine. Yes the brush has to be hidden when looking at the closed door from both sides. So, it has to be thinner than the door brush. To make sure it seals the door opening , you can filter out entities. Also, filter out detail and patch mesh to make sure the room is structurally sealed.
I just tried compiling a small test map with my new Dell 3.4Ghz computer. The DOS compile screen blinked on and off so fast that I was not sure it even compiled, but it did. That map took about 5 minutes to compile with my old computer (Dell 733Mhz).
Once again I'd like to thank you for your advise. I've used the detail brushes & the 'no draw' texture. Compile time has been cut down to about 1.5 hrs!!!! WHAT A DIFFERENCE!
The folks over at www.crazycampground.com are going to run it this weekend to test it on a server. If all goes well, I'd like to know where I could upload it for more people to use. Any suggestions?