Anything is paintable. It's probably a baked enamel finish, just clean really well, let dry and paint with alkyd enamel, possibly two coats if it's a color change.
Rollers and brushes, you don't say what the height is. A friend of mine used to paint the poles on the big billboard structures going up and down Interstate 95 about 150' up. He said the wind could catch the paint from the paint bucket to the pole and blow it 100 yards, he's cleaned many cars with paint thinner. It's going to be sloppy no matter how you do it, may want to sub it out to a painting crew.