I chilled the tier again in the freezer for about 15 minutes to firm it up after combing it. Then I put a thick layer of lighter pink frosting around the middle of the cake.
Then I wrapped the bottom of the tier in the last darker buttercream. Spread it thick enough to smooth with a bench scraper without ruining the other icing layers.
For our test, we put the cake in the fridge overnight, and the next morning it still looked good. Of course you can use a flower water pick or tube if you want to!