A better way is to cut out the section of the wall that is not painted. Grab some painters mixing sticks. Say the square hole you cut is 5 inches, cut and stack the mixing sticks to 7 inches. Slide the sticks behind the wall leaving 1 inch on both sides of the wall and secure with drywall screws so that you can see the sticks through the hole. Do this to the top and bottom portion of the hole you cut in the wall. Or left and right depending where your studs are. Lowes sells scrap drywall, at least mine does. Cut a piece of drywall to fit the whole you cut out. Cut a small piece from the 12 o'clock part of the new piece to the middle for the wires. Fit the new piece inside the hole and secure to the painters sticks with dry wall screws. Spread mud, sand smooth paint stand back and profit.