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]
(..) Someone need a hand? -Where's my nose? -Here it is. -Here's your arm. -Give me that. That's mine. Honey, the mustache? l don't recall playtime being quite that strenuous. Andy never played with us like that. We're just gonna have to make the best of it. (..)2010 Toy Story 3