Paint shakers, also called paint tumblers, are designed to blend paints, varnishes, primers and more finshes completely. Good paint shakers utilize 3 dimensions of mixing - orbital, side to side and up/down. To achieve these multiple motions, Tornado II shakers spin an eccentric fly weight rather than using crankshafts, belts, or pulleys which can wear out and break.
The antifouling in bottom paint is often heavy and will settle to the bottom of your can. Make sure you take the time and effort to mix your paint properly. If you have a paint shaker, run it for at least 5 minutes to get the copper and the pigment evenly distributed throughout the paint. If you are doing it by hand pour half the paint into a mixing bucket so you can mix without making a mess. Keep dredging up the copper off the bottom of the can until the bottom feels clean to the touch of your paddle. Slowly stir in what you poured off until the paint is uniform in color and consistency. Each time you add to your roller tray you will want to quickly stir again to ensure consistency.