I've got a good gun for final paint, but have used several Harbor Freight guns for primer etc. I've also used them with acrylic enamel, lacquers and urethanes with good results. I'd have no problem using one of their guns to paint the bottom of the car. I think the painter has more control of what the paint job turns out like than the gun. I probably use a Harbor Freight gun more than my Sata because I want to keep it in top shape for the paint jobs that really count.