Thanks for the suggestions so far.
Folks I do color and B&W, but this is more for color, and my goal is to drop the transparency on the light table and have the final image with no or very minimal manipulations needed.
What I really would like to know is if there is an easy way to match the contours of the scene in front of me when making the mask? Or am I faced with a frustrating process that is time consuming an fraught with imprecision? From my experience I think it is the latter, but if anyone has tackeled this problem and solved it with a modicum of success, please let me know.