How about:
The roof and windowsill-Fill with white glue with a toothpick, then paint to simulate bird droppings.
The walls-Bullet strikes.
The street-A little dirt, a little rubble, etc.
Having used drywall for streets, buildings, etc., I've found that the plaster has a lot of natural defects, not unlike what shows up in your pix, so it doesn't look that bad to me, But it's your call. Let's see it when it's done.
Art