I have been having similar issues with air bubbles under buttercream icing. I chill the uniced cake over night and then ice the next day.
When the air bubbles arise, I use a tooth pick to break the air bubble and then smooth out with a paper towel and fondant smoother, trying to work out the air.
I use an icer tip to put my icing on. Lately, I have been putting the thinnest coat of icing on as a crumb coat. Sometimes I put the last layer of icing on with a icing spatula, sometimes I use the icer tip and then smooth it out with a spatula.
Lately, I have not been having a problem with it, but the weather has cooled down quite a bit.
I hope this helps.
P.S. I do not consider myself an expert! Just someone who has a passion for creating cool cakes!
Psalm 127:1 Unless the LORD builds the house, the builders labor in vain.
