Hmmm. Post up some pics of these various things and what you've got built so far. We'll see if we can get you some similar project pics to get you going. Don't go anywhere near anything with the alleged plastic cutter- those never work well.
I used the editorial "we" there, by the way.
+1 to this. I built most of my cab using Saint's book. The bezel area is one of the places I felt the book was mostly silent. Having actually put my monitor in and looking around the forums, I know why. Depending on the bracing you went with for your monitor and the type of monitor itself, there are a million different ways people tackle the job.
I cut my bezel using 1/4 ply. It fits very tightly in the cabinet right up against the monitor. I painted it black and attached the smoke plexi to it. What holds it in place is an aluminum L bracket. Here is a pic.

It is very sturdy, and because of the way I put it in, I can easily remove it as well. Once again, though, so much of it depends on what you built.