How can I get the Moustachio achievements in Left 4 Dead 2?

Yes,

• Gong Show: You need to inject an adrenaline and hit the gong at the strong man game, see here
• Stache Whacker: You need to quickly hit the Moustachios on another game (don't know the English name), see here

I got them both, it's not difficult.

You can get Gong Show by getting a tank to hit the gong for you. Much more fun than using up your adrenaline!