As long as you have the deck totally clean(free of old paint oxidation dirt and the such)you should be ok to go. If you are worried about the smoothness of the paint job use a primer that works with the base coat your using. Take your time and leave at least 6 to 8 inches between the can nozzle and the deck move at a steady pace from left to right keeping the nozzle at the same distance, follow the curvature of the deck. Spray on coat evenly and then let it dry, before adding the other coat, DO NOT LET THE CAN STAY IN ONE PLACE FOR ANY AMOUNT OF TIME OR YOU WILL GET DRIPS AND RUNS. Try to keep the can moving at all times. This should help you obtain a lovely finish.