The messy frosting (or Spackled as I like to call it) takes more than just slathering on frosting. Without a good base your cake will end up uneven. When I use this technique I start out with a smooth frosted base (go HERE for the tutorial) this is more than a crumb coat, you need to really even out your cake. Once it is frosted and chilled I take out the layers one at a time starting with the base. That way they remain chilled and firm as I spackle on more frosting!
I just pipe simple dots 3 at a time up the cake- then use my little spatula to spread them, they will set up quickly. It’s easy if you have a good (chilled!) base.
For my latest stacking helps go HERE.