I don't recall seeing it mentioned. Also he said it's mostly a weekend car not driven much, so I assumed the problem was on the inside. If that's the case my mistake.
If on the exterior, I trick I was taught by a local detailer was to use chrome polish on the windshield, wipe in on, let it haze....wife off with MF towel and it takes all the crap we put on the windshield off and leaves it clean as a whistle.