Since you seem to be on a 101 uses for tin foil theme at the moment I'd love to see if you can find an easy way to produce 4mm corrugated iron using it. I've had great success in 16mm using a readily available crimper, but there doesn't seem to be a small scale equivalent.
My method evolved when I needed some corrugated iron but had no money as a youth. With a large building I wanted to cover, I spotted that the roof of a recently bought Wills kit for a scrapyard might act as a press for me to make my own from tin foil.
Most of the kit has long since gone to the great model shop in the sky but the roof remains. Any time I need corrugated iron, I whip out the tin foil, cut it into scale 6 X 2 sheets and press these into the roof with my fleshy fingers.
Maybe the result isn't quite as clearly defined as plastic or a proper press tool would achieve, The sheets are pretty fragile too - poke one and you'll squash the corrugations - but it is stupidly cheap to do and looks the part on a model.