[E-40six]

ex-painter here

draw out a square outline, then score the line with a utility knife. then take drywall knife and cut along the lines. you'll hit a joist but dont worry about it. once you made the cut, just pull it off

now when you replace it, measure your hole, cut a piece of drywall the same size you took out and screw the new drywall into the joists.

If the hole is not spaced correctly and you can't get a good bite on the joist, add 2x4 to the joists so you can screw the drywall on it