I am with HRP , paint them individually , that way everything gets paint on them , including the edges.
I would find a couple of extra friends to come over and help hold each panel while you bolt things together , use a couple of layers of masking tape or protective tape to tape off areas where the panels may touch to help keep scratching to a miniumum.
It may require a bribe of some free beer to get them to help , but only after the job is done! That way you all can stand back and admire a job well done

SprayTech