Duke William of Normandy won the battle because was well prepared and had a good army. They prepared carefully for the battle. The Normans had knights on horseback who were skilful fighters.
A utility knife, metal ruler, and a hammer can be faster than trying to carefully saw an opening. Score the drywall a couple times till you are most of the way through, then just knock a hole with the hammer and break the drywall back at the score lines.
Full-sheet repair: This is the simplest ways to repair large holes in drywall. The sheet is removed from the studs and a new piece of drywall is screwed in place. The joints are taped, mudded and sanded, resulting in a clean repair that might blend better with the rest of the wall than a small patch.