She tried to 'smooth things out' [=end an argument or disagreement] with her daughter-in-law, but the damage was done.
They 'smoothed the way' for a quick end to the dispute. [=they made it easier to achieve a quick end to the dispute]
Her time at college wasn't all 'smooth sailing'. [=she had some problems/difficulties during her time at college]
(..) I am an ogre! And guess what, Princess? That's not about to change. I've made changes for you, Shrek. Think about that. That's real smooth, Shrek. "I'm an ogre!" I knew this would happen. You should. You started it. I can hardly believe that, Lillian. (..)2004 Shrek 2