talk through one's hat
chew one's ear off

No, I used to talk through my hat quite enough in the past.

"And I may well be talking through my hat, is what you're thinking."

And yet they didn't have any signs so I think he's talking through his hat.

"Somebody who didn't talk through his hat, you understand," Tooney added.

So you think perhaps Charles wasn't just talking through his hat to impress her?

"I believe you're just talking through your hat," said Japp.

Ken was talking through his hat, and you know it.

Some one behind him said: "Talking through his hat."

But if I said any more than that I'd be talking through my hat.

Talking through your hat is supposed to mean you're hiding something or making something up.