Recently, I had to finesse a small piece of drywall into place as a patch. As I began fitting the drywall into its opening, it became clear that I needed to trim a bit off one corner. Normally, I use one of those cheese-grater gizmos for this task, but mine had gone MIA.
Rooting around in my toolbox, I found an old reciprocating-saw blade. I dragged the tooth side of the blade across the edge that needed trimming. The teeth cut shallow grooves in the drywall. Dragging the back side of the blade across the grooves knocked down the ridges between the grooves. It went fast and was precise, perfect for small patch applications.
Frank DuBois, Deale, MD