Thinking of covering a cake with it. Id love your help!
Well...........I find it tooth-hurtingly sweet, so I only use it very rarely for accents and as a thin covering on spheres or very odd shaped things.
I always roll it between 2 sheets of parchment, chill in the fridge for a few minutes, and then use the warmth of my hands to mold/smooth it.
Look up the Klara Johnson books, they have detailed information about using rolled buttercream. Look in abebooks.com for used copies.
Marsha Winbeckler also has a book on it. And there is a video/DVD on it.