I first experimented with greenstuff for flags and banners early 2011, as I had a long strip of greenstuff I'd bought and discovered I hated using the stuff on figures (too much like used chewing gum...) and was wondering what to do with it. Turns out it makes very nice, strong banners and flags! Mold ripples and folds in, and you get a flag that's more 3d than paper and more resilient than metal foil. The thin greenstuff is still flexible, so you can even gently flatten some of the ripples out to make painting easier.
I did eight in a variety of sizes and proportions before getting bored of wrestling with greenstuff and turning the rest of the lump of putty into the start of a rough rock wall. Eight will get me through the current and short-term RCW plans and leave some left for other uses, too. Perhaps I'll do a flag for my tropical interwar Brits, although that would involve freehanding a pair of Union flags, and I'm not sure I'm that insane...