I should clarify. Three THIN coats of buttercream. First is the crumb coat (and for mine, I still have some cake exposed because in this stage, I want to make sure my dams are holding in the filling), the second coat covers the whole cake so that no cake is exposed. The third coat covers the cake evenly. (I sometimes do a 4th coat to get it perfectly smooth with my straightedge and then I cover with a thin layer of buttercream. I've never a problem with there being too much buttercream on the cake so when it comes to room temp, no issues :) I've attached a picture of cakes I had in the fridge last summer that just happened to be coated differently! Then, you can see the finished product of a slice of cake at room temp :)
As a side note, if I'm not using filling in between the layers of cake, I only do 2 coats and make sure to get the straightedge out for the second coat. In between the coats of buttercream, I refrigerate for a few hours though to make sure the buttercream really crusts over.
I hope the visual helps! :)