Please tell me if I'm posting in the wrong place.

Many a time, I've found myself in the situation where a friend, feeling that he can't approach a girl on his own, asks me to wingman for him.

I have no problem going up to strangers and initiating a conversation, but I don't know how I can properly talk up a friend. Any time that I've tried, I just end up sounding ridiculous.

Is there a way that I can make a friend seem desirable, without sounding like I'm holding his hand and talking about what a good boy he is? Furthermore, can one wingman for a friend without making it painfully obvious that that is exactly what he's doing?

Should I talk them up a lot? Introduce them and feck off? Just be plain friendly and hope that something sparks?

[If at all possible, try to account for possible differences in culture. I live in West Europe, bouncing back and forth between Ireland and Portugal.]

Tl;Dr How can I wingman for a friend without sounding like an idiot/being creepy/being too obvious?