Polar Direct To Metal Paint

Direct to rusty metal paint with preparation and application guidelines that look pretty similar to the better known Smoothrite. It sprayed OK and the finish looked nice, but despite preparing my rusty swingarm according to the instructions, the rust was already starting to show through again after a week - and the bike hadn’t even left the workbench - so can’t really recommend it.
It is, however, cheaper than the aforementioned Smoothrite, so it's up to you. You may get better results than I achieved.
Around £15 for two cans from AMAZON.

I couldn't get a decent photo to show it, but rust is already making a reappearance in the really pitted areas.