I use this method all the time, with great success. Make sure you are using a crusting buttercream icing (like the Wilton Decorators icing recipe, only use all shortening for a good "crust"). After icing your cake, let sit for 10-15 minutes so the icing will "crust" (which means it gets a slightly hard surface on it). I then take a VIVA paper towel and rub sides, moving hand up and down, then in small circles, then gently lifting paper towel and moving on to next area. (You will need to get a new paper towel as the old one absorbs oil or icing particles.) I do my top in a side to side motion with my hand to smooth out. Finally, I let my paper towel "drape" over side of cake so that 1/2 is on top of cake and 1/2 is on side of cake. I then take the forefinger and middle finger on each hand, placing one hand on top and one hand on side of cake and rub the edge of cake between those fingers. Fingers will be placed in the position of an upside down "L" shape. This will give you a crisp, defined edge on you cake. Hope these directions are clear enough to understand. Good Luck if you try this method, I think you will like it.