I just roughly calculated how many windows we’d have to paint on cardboard boxes to make a city.
Eek.
You’d need some very cheap basic grey paint for the base coat (emulsion? poster paint is probably too thin) and a spraygun would help, or else a big brush, and then probably use some sort of sponge stamp to place black-paint windows. Maybe get a piece of wood 30cm long, glue a whole row of foam squares to it, and use it to stamp a row of windows at a time…
I wish I had time to play with this. But I have a spawn instead.
Incidentally, we had a cute dinosaur costume for little Cathy (suit 18 months) and she was an excellent demolitions operator. But Meiling gave it away…