Hanriots would be fun but I wasn't sure how many people were interested in Italian/Belgian planes.

They've got a bit of gloss.... But then, so did a lot of actual planes, due to the coatings they'd put over the paint (e.g. linseed oil). I'd describe it as "satiny", as the surface doesn't look polished so the reflections are not uniform.

A matte coat spray would almost certainly work, but I'd recommend testing on a small portion of the underside in case it acts as a solvent or something, since I don't know that anyone has tried it.