To fluff a flocked Christmas tree, you need to shake the branches gently to loosen the flocking and create a full, fluffy appearance. Be careful not to overdo it, as too much shaking can cause the flocking to fall off. You can also use a soft brush or cloth to gently brush the flocking into the desired shape. Additionally, you may want to consider adding some ornaments or lights to add even more texture and interest to your tree.