Back on topic:
I inspect my bikes every few months for paint damage. When I find some, I rub down with emery cloth, and patch up the damaged area with a paint that goes directly onto metal. I generally apply two coats, sometimes it needs three.
I have 3 colours, red, blue and black.
When the bike starts looking too tatty (except sometimes for the gloss black my colours never match factory paint exactly), I use fine emery cloth to roughen the surface and repaint the entire frame/forks using the old-fashioned paintbrush method.
Not yet had to do this to my Thorn bikes, which are all relatively recent. My 2009 Brompton got the treatment a few years ago (folders take more knocks in my experience) when I decided the mottle effect of gloss black patches on the matt black original paint had gone far enough.
A possible disadvantage of this method is that any decals, stickers, etc. are lost, but I don't really mind if my bikes become anonymous to others, I still know what they are.
