Ok - all you pro painters out there. What's the best solution / system to use when painting the undersides of new steel wings? should all that thin black paint (is it paint - called Phosphoretic?) be removed? or is a good dry prep good enough to key? Should we be using 2 part epoxy primer followed by 2 part epoxy gloss? Or is there a better system?

You can paint over it with solvent or waterbased paints, no problem but on the underside you might be better off with waxoil or ziebart type product. I'm not a pro so I use ruberoid type paint from Wickes or similar under mine.

Just colour the outside and wax the inside