Put it right after the moustache reveal in your edit, preceded by Eww Brother Eww for the initial reaction, then follow it with Nelson's Ha-Ha! to close the roast before you cut back to the main scene.
Über diesen Sound
A short three-second French voice clip delivers the line naming Martinez and his terrible moustache, spoken as a blunt put-down. The tone feels mocking and amused rather than angry, turning a simple insult about facial hair into a quick, dismissive laugh that lands as pure teasing.