Even though my butter was softened, when I mixed it by hand it was hard to get the butter to blend well, then I didn't know if it was butter or bananas I was
mashing against the side of the bowl (you may laugh at me now).
You do actually want to get a lot of the air out of the mixture — you do this by folding and squashing the
mixture against the side of the bowl, rotating the bowl a quarter turn with each fold.
You would think that cracking an
egg against the side of a bowl is the best way to avoid eggshells from getting into your food, but that method actually splinters the shell and creates more errant shells.
Since it is 2 years later that I found this, it is probably too late for you; however, for anyone who wants a smoother finish: dip your brush in water (I used an old plastic bowl), drag the
brush against the side of the bowl to remove some, then dip the brush into the paint.
Mix these together with a fork, mash
it against the side of the bowl until it becomes a crumbly mixture.
In a small bowl, cream the soft butter by beating
it against the side of the bowl with a wooden spoon until it is soft and fluffy.
Slice the ripe bananas and add slices to the bowl with the chocolate and use a fork and mash the banana slices up
against the side of the bowl.