This idiom means "Talking a lot without significant results". I was wondering if there was a specific idiom to say this. So far, I have found nothing but "hot air merchant".
Wikipedia suggests that the word is particularly associated with political speeches in Ohio, and U.S. President Warren G. Harding was particularly good at it.
Hot air is an expression that means
Empty talk that is intended to impress.
- ‘they dismissed the theory as a load of hot air’
We generally say someone is full of hot air
Talking a lot, especially without saying anything of value or meaning.
- Did the salesman tell you anything new, or was he just full of hot air?
or that they are blowing hot air
A person that has a lot of verbal wind that likes to sound off