Are you sure you want to delete this?
May I throw in my 2 pence worth.
You have not mentioned who actually owns the helmets. You can reduce the reflection by rubbing the surface with “flour paper”, it is a super fine sand paper that etches the surface and stops reflection. You can also use a car product known in Europe as “G3”, it is an abrasive polish which you use after spraying a car, on plastics it will stop reflection. With these products you can reverse its effects and put the shine back in after you have finished using the props. So nobody will know!
You could light the interior of the helmet to maximise the effect but if these are dialogue scenes, you don’t have to concentrate the camera on the face all the time as the astronaut will be moving due the zero gravity effect. I would deface the helmets glass and light the interior with a LED and gel to taste. You need to get the balance right to create a clear image of the actors face as it depends where you placed the LED. Old Christmas lights will be the best and are easy to hide. Photo attached on how the effect should look.
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