One of the problems I encountered the most when I first started out was that of getting a good coat of frosting free of crumbs. And the further along in the frosting process I got, the more the issue snowballed. Crumbs got back into the bowl and were then just redistributed all over the cake each time I applied more frosting. It would quickly became one, huge crumb-y mess.
The easy fix for this is to do what is known as crumb coat. You lightly coat the cake with a thin layer of frosting, not worrying about any crumbs that might get in the frosting at this point. Then you stick the cake in the fridge so that the frosting will set. When you put the final coat of frosting on the cake after it's nap in the fridge you don't have the worry about the crumbs because they are sealed in under the crumb coat.
PS I've never really tried to smooth the frosting (I like that rustic look that comes with imperfection..it just seems more "homemade" for some reason), so I'll have to do a post on that soon.
The crumb coat is imperfect, but that's okay but
it simply seres to seal the crumbs in place.