I’m a bit unsure if the protective spray should be used and for which paper. I can only get Hahnemyhle protective spray here. I have ordered Canson matte paper and Hahnemyhlen Baryta paper. Baryta’s surface structure can be quite sensitive to scratches and fingerprints.
Another thing, which printer paper setting should be used for thick 0.5mm matte paper. Canon Pro300
I’m not up to date on fine art printing, but as of a few years ago there were several protective sprays available and they appeared to be interchangeable. It would be a good idea to contact the manufacturers to be sure. Those are wonderful papers! The Baryta was a favorite for the rich blacks.
I would check with Canon on the printer settings. Thick papers can damage a printer (and smudge with inks) if the wrong hardware settings are used.
Hahnemühle’s protective spray is fantastic and it’s what I use for my prints. I print on Hahnemühle Photo Rag Baryta paper, which has a luster finish. For me personally, the primary reason I use the spray is to cover up any bronzing and gloss differential. Once the spray has been applied, the print looks like a darkroom print because it’s perfectly consistent throughout. You’ll definitely want to test the spray on a paper to see how it reacts, but for the paper I use, the prints look even better after the spray has been applied.