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.
When you are ready to install the drywall you will need to use screws or nails to attach it to the studs of the room and then fill the seams between the pieces of drywall with joint compound. In comparison to traditional methods such as plaster, drywall is far easier to install and to perform drywall repair.