Whatever you do to it, keep in mind that it will continue to weather once you put it outdoors. It looks like it has a fair amount of bare rusted metal that should be protected from further rusting. Three or four years outside and it will have weathering showing up again.
To answer your original question. I worked at gas stations in 1967-1968. A couple times a year the islands and pumps were painted by brush. They looked good for a couple days until someone spilled some gasoline on them then they got the crinkled paint look.
