[SOLVED] how to use swap buff?

So far I haven't been able to use swap buff. I was told that if I fall down a cliff and use it, then I'll swap body with my opponent, who will then be the one to fall.

How do you "use" the buff? How to you choose whom to swap with?

Does anybody have a video of how it works?

Nearest opponent.

I run towards Ernie when I have the swapper buff to make sure he is the nearest opponent.

Yes, I like to use it against him.

Thanks, Julius. To add information for those who are also wondering:

After you get the swapper buff, you can use "drop weapon" (default key: "g") to activate it. When it's activated, your position will be exchanged with the nearest opponent, as Julius said. He likes to jump into the void and then swap with his opponent, who then will be the one to fall.