When I first watched the video below I didn’t fully understand some “What, How and Why” because I was just a beginner with 2 months of experience or so…
Now that I have almost 1 year “playing” with Blender, I can fully understand it !
Highly recommended for hardsurface modeling with holes!
Note: For those that don’t get it, he made a backup of the mesh (which he calls “guide mesh”), copied and then made the holes. He shrinkwraps the mesh with holes to the mesh that doesn’t have it.