What does "in a sandpaper-dry kind of way" mean?

Question

He was the quintessential newsman: cynical at times, but unrelentingly curious and full of life, and often hilariously funny in a sandpaper-dry kind of way.

Could you tell me please what it means?

Does it mean:

His laughting made noise like lustle of rubbing a surface with sandpaper.

The fuller text:

When I began my career in journalism—I was a reporter at a national magazine in those days—there was a man I’ll call Claus Schmidt. He was in his mid-fi fties, and to my impressionable eyes, he was the quintessential newsman: cynical at times, but unrelentingly curious and full of life, and often hilariously funny in a sandpaper-dry kind of way. He churned out hard-hitting cover stories and features with a speed and elegance I could only dream of. It always astounded me that he was never promoted to managing editor.

Answer 1

It refers to "dry" or "deadpan" humor : marked by a fixed air of seriousness or calm detachment.

By using "sandpaper-dry" instead of just "dry", the author tried to convey that the newsman's sense of humor was not just a little dry, it was very dry and maybe "gritty" which is also used to describe humor (in the sense of having strong qualities of tough uncompromising realism).

Here's another example of the same usage from Paste The 25 Best Comics of 2016:

They’re silly, but in a serious manner, where a sandpaper-dry delivery renders the absurd amusing.

Answer 2

"Dry" means he is funny in a specific way, which is quite hard to explain, actually. It is a fast, unexpected and often witty response.

Answer 3

I would not say it means dry, but rather slightly grating.