Countless franchises have forums dedicated to making accurate costume replicas, and the 405th is home to such forums for Halo. User Redshirt posted a tutorial about making a see-through visor over five years ago, but it’s still relevant and helpful. This visor was used for a Halo costume, but you can obviously adjust and use the tutorial for other builds.
It all starts with a pair of outer visors from the MC-2AP chemical defense masks. You may be able to find the mask at your local surplus store or on eBay. If you can’t locate the mask, that’s okay. The techniques Redshirt discusses will work with any hard plastic. The first step is removing the visor from the mask. Redshirt used a saw-toothed cutting wheel on a Dremel while wearing safety goggles.
Several steps later and this is how painting starts:
All right. For all of you who never had any intention of using a chemical defense visor in your helmet, but just wanted to know how to paint your own see-through visor, here is what you’ve been looking for. The first step is the reflective coating.
The end result you need to achieve is a very fine, very even, and very thin coating of reflective metal on the outer surface of the visor. Everything you do here is driving toward that. Beg or borrow the best air brush you can. I did my first attempt with an old Testors brush with a leaking air valve that caused the paint to spatter. I borrowed a brush locally (apparently I’m not the only person that deploys with an airbrush) that turned out to be only slightly better. You really need top performance for your first job of applying the Testors Model Master Aluminum Plate Buffing Metalizer. Be careful not to purchase the non-buffing Aluminum
Metalizer. You’ll need some of the special paint thinner that Testors makes for their Metalizer line.
Read more at the 405th forum. The tutorial is extremely thorough.