He used a small pair of scissors to trim his 'mustache'.
The actor was wearing a false/fake 'mustache'.
a 'mustached' man [=a man who has a mustache]
(..) Yay! We can improve. Let's think about it quietly. (groans) (sniffing) Boy, I bet that mustache smells really bad, huh? Oh, don't you rip on my lip strip. (sniffs) I smell candles (..)2016 TvShow: The Simpsons Title: Fland Canyon Season: 27 Episode 19