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.
Use the 8-inch drywall knife to load some drywall mud into the mud pan. Dip the drywall knife into the pan and scoop some mud onto the knife. Start at one corner of the ceiling and apply mud to the ceiling with the drywall knife. Apply the mud while holding the mud knife at approximately a 30 degree angle.