If the gel coat is shiny, there is no reason to buff it. A good coat of marine wax is all that is needed. If the gelcoat is oxidized, and has a dull or chalky appearance, that is when you need to break out the buffer, and polishing compound like Aquabuff. And the buffer should be a decent dual action or rotary with wool pads. Those orbital polishers, that just vibrate a little bit, aren't going to do much good.