Hello! Smug is an adjective that describes an attitude so I think it would better to say "smug look", "smug attitude" or "feeling smug". Here are some examples: "I wished that he would wipe the smug look from his face." "It was obvious to see her smug attitude as she took over the conversation". I hope that helps!

Takashi pushed Misa over with a Smug face. (example scentence.) Smug face is usually not a good thing. It's used when someone does something rude and they feel superior normally. Its basically a "I'm better then you" look that people give. It's generally rude. So like if you you were trying to tell someone いけ！You might do it with a smug face.