I made a sponge cake for my Aunt & Uncle's Diamond Wedding Anniversary a few years ago. I covered the cake in butter icing, let that set a bit (so it was 'tacky' to touch) and then put ready-roll icing on it. It wasn't perfectly smooth, but it looked quite good - even if I do say so myself !
If you're using glace icing then you might want to go with the glaze to help keep the crumbs down.
Sorry not to be more helpful - I can make cakes but am not good at decorating them in the main.