I would seriously polish it and see how it comes up. As Jwalker points out it quickly passivates then its virtually maintenence free.
painting may seem like a quick fix but once its painted you wil need to keep painting it as damage occurs.
if you do paint it to do a really pukka job you should get it media blasted, leave to passivate a few days ,acid etch primed, then painted with a 2pack epoxy or PU. powder coating is fine too if its done properly, and as NOS observed it rarely is.
To be honest to paint it properly would cost near as much as a new A frame, I see Halfrauds do sell acid etching primer in aerosols £10 last time i looked, may be worth a try? with top coat of your choice as a cheap DIY job!
I am usually not as green as i am cabbage looking.