Maybe try this, a Gimp brush dither.gih (gimp image hose - an animated brush) this is just pixel dots scattered around and it might get you your "distressed" edges.
Use the pencil tool to keep the hard edges. Unzip the attached, put dither.gih in your brushes folder, Refresh brushes or restart Gimp.
Another quick example. https://i.imgur.com/c5M46Hy.mp4
Use the pencil tool to keep the hard edges. Unzip the attached, put dither.gih in your brushes folder, Refresh brushes or restart Gimp.
Another quick example. https://i.imgur.com/c5M46Hy.mp4