I make a big batch in my 5 qt mixer. It gets the level of icing well above the paddle while mixing, and you get very little to no air bubbles in your icing this way. It is important to start with an icing with as little air as possible; so i fill my KA to the rim with this recipe:
5 1/2 cups hi ratio shortening ( sweetex)
5 pounds sifted powdered sugar
liquid which consists of 1)flavorings and 2) a liquid I make by mixing powdered coffee creamer, one cup to one cup hot water. I make this liquid up a few cups at a time and keep it in the fridge till I need it.
I let it go for 5-7-minutes till creamy and smooth on about speed 6.
I ice the tops of my cakes with the open coupler in a pastry bag and give it a quick smoothing with a hot spatuala ( dry, not wet). I then ice the sdies regualry, then use my bench scraper to smooth out the sides. after that I pull the excess icing along the top edge in toward the middle of the cake . I get down eye level with it to make sure that top edge is level all along and not waving. i then use viva with my hands, then viva with a fondant smoother and then computer paper with the smoother to give the final smoothing; which really is the magic touch.
I hope that helped you some!!! Its hard to explain without seeing it!