It just gets way confusing when trying to explain this to non-super fans. **Holds up a custom mandalorian helmet** "This is a mandalorian helmet" **Holds up The Mandalorian helmet** "This is The Mandalorian helmet, it is a mandalorian helmet, but specifically The Mandalorian helmet." friend then asks, "Is Boba Fett's a mandalorian helmet" I exaplin, "Yes and no, he does have mandalorian armor, not to be confused with The Mandalorian armor, but Boba Fett is not a mandalorian" I start to see more confusion come across my dear friends face. LOL
Oh yeah, totally, didn't mean to imply you can't shine up cold casts. Definitely doable with really great results, just takes a lot of polishing work though. So I'd suspect for a film production where'd they'll likely have many hero and stunt copies, it'd be easier and more consistent to spray a metallizer on them. Just what I suspect the prop artists did.
But yeah, tons of different methods that us reproduction builders can use.
I agree, I think cold cast will leave a "brushed" look to the armor. While a product like alclad or spaz stix wouldn't. There are even the spray on chrome products similar to what is used in this video. The Captain Phasma community would be a good resource for chroming methods.