Since the buttercream was slightly cool still, I put it in a mixing bowl to fluff it up a little bit before piping with it. You don't need to whisk it again, the paddle attachment for the mixer is best. I started on a low speed and mixed it until it became a nice creamy texture that would flow evenly from my piping bag. If I had a good emulsion when making the buttercream the other day I should have no problems now. An emulsion is a mixture of fat or oil and water. In our case butter and egg whites; there is water in the butter, egg whites, and sugar syrup. By whipping them the milk fats in the butter were forced to clash with the water. The protein in the egg whites help absorb some of the moisture, aiding in thickening process.
Next were shell borders. These two take a lot of practice. It seemed that with each row my shells were loosing their shape. By this point I had been piping for at least 2 hours and my buttercream was getting soft. To keep the buttercream piping smoothly and evenly you can put it back into the cooler for a couple minutes, to let it set a little. The key to the shells was again the movement of the wrist. It is an up and down action of the hand, not of the arm or whole body. The tip should be at a 45 degree angle following a "pipe, move back, then move forward" action. The next one in line should be started 1/3 of the way on the one before. I also attempted a tear drop border which like the shell took concentration and precision. The key to the tear drop was that you wanted it flat, no height because the bag was moving horizontally not vertically. Most of my problems came from pulling the tip to abruptly down after piping, making very deep lines that were rather unattractive. This skill will definitely take more work to master!