PennCentral99 or you can use a toothpaste tube squeezer or paint tube wringer. They're $10 on amazon https://www.amazon.com/Toothpaste-Squeezer-Wringer-Artist-Painter/dp/B01MT2A6WP/ref=sr_1_1_a_it?ie=UTF8&qid=1535227906&sr=8-1&keywords=paint+tube+roller Terry
or you can use a toothpaste tube squeezer or paint tube wringer. They're $10 on amazon https://www.amazon.com/Toothpaste-Squeezer-Wringer-Artist-Painter/dp/B01MT2A6WP/ref=sr_1_1_a_it?ie=UTF8&qid=1535227906&sr=8-1&keywords=paint+tube+roller
Terry
I prefer to use "corrugated" sheet styrene. Not only does if give you the desired surface finish but it doubles as the structural component. It's difficult to damage, too. Want the look of individual panels? Just scribe the styrene to define the panel edges. Add paint and rust-colored weathering approaching the lower edge of each (or some) panel(s) and you'll catch your layout visitors touching your structure trying to determine whether it's really individual metal panels or not.
Hornblower
Many years ago in the kinks column in MR it was suggested that using a file for the base and a piece of wood drawn across the aluminum foil on top of the file would create corrugated siding.
ndbprr Many years ago in the kinks column in MR it was suggested that using a file for the base and a piece of wood drawn across the aluminum foil on top of the file would create corrugated siding.