Depends what paint and how old the paint is if buffing will do anything. There are enamel single stage paint and there is urethane single stage paints. Old weasthered cheap enamel single stage paint won't buff out no matter what you do. Depending on the age and weathering on a urethane paint you may have a good shot of wet sanding with 2000-3000 grit paper to knock off all the roughness and then polishing.
Depending on how good the paint is you could always wet sand and put a good urethane clear cost on top.