Reading up on some stuff I got off the Net on Mastering. The guy bounces his stereo mix down out to a high resolution WAV file and then brings it back into the DAW to do the mastering. To me that seems one way to do it, but another method would be to leave all data and tracks intact within the project. Set everything to mix down to a stereo output and then apply your mastering technique to that stereo output. An advantage to the later method would be that you could go backing into the mix rather easily and fix something at the track level.
Thus I am wondering what method you might use from above, or if you do it differently then how are you going about your mastering?