So you are looking for a free magic solution?

I mean, I like houses made from big stones but it is probably cheaper to paint an existing house, instead of tearing it down and replacing with stonewalls.

Probkem is that it does not scale globally if you can only rely on short term efficacy

The surface finish of walls may also make a difference. Rough vs smooth and something like that doesn't fade as quick as paint itself.

No solution is free and needs no replacement.