How Do you clean Theater Port Glass?

I had a request today to clean the “glass” the projection screens display through in theaters.
The manager said he’s not exactly sure if it’s glass or plexi glass. He said the rooms with the 3D monitors have a tinting on them.
He said he tried (and showed me) all sorts of different micro fiber clothes he’d tried using but how there was still a film on the glass. It looked to me like it just needed to be squeegeed and it sounded like they only tried alcohol based products like windex.

It shouldn’t be, but it was tricky to tell if it was plexi glass or real glass. One pane I looked at looked like it had scratches like I’ve seen on plexi glass before.

Anyone have insight into a situation like this? Has any cleaned theater “port glass”?

I cleaned a chain of theaters years ago and did all the projection room windows on the theatre side. Just use traditional method with gleam.