Looking forward to seeing how the Torpado turns out! That should be a good candidate to paint with a brush because you won't have to worry about so much busy masking work that it would require if sprayed.
I paint a variety of things, from landscapes on canvas to model kits to reproductions of ancient artifacts, yet for some reason I've always been put off by the idea of brush painting a bicycle frame simply because that's "not how it's done." I remember seeing your PX10 and thinking it looked fine, and have seen enough original vintage frames where at least the lugs or panels were hand painted, so I decided to give it a go recently. I'm almost done with a full brush "touch up" job on a 1979 Mercian that will end up covering a majority of the frame to hide the fact that my red was not a perfect match!
I actually opted to use Testors enamel paints that are meant for model building and such, which come in tiny bottles for $2 a piece at hobby stores. So far I've gotten two or three coats over almost an entire frame set for less than $10! The stuff sands nicely and dries relatively hard, and I'll seal it with one of those fancy rattle can 2k clear coats. It's been such fun and there are so many color options with the Testors enamels (many of which can also be had in small spray cans) that I'm considering picking up another frame just to do it again.
-Gregory