You can actually do it all by your lonesome in your garage. You have to make a vacuum chamber big enough to hold the visor (cheap!), generally a 1/4"-1/2" walled 16" ID x 2' Steel sewer tile oughtta serve as the main body and a couple of 1" thick acrylic squares that cover both openings in the sides of the tube for side walls. You need a sufficent vacuum source and a rack to hold the visor above something like a lighting element for a huge street lamp (generally made of tungsten) and a source of electricity that will heat the element sufficiently (basically, enough wattage to power it on white hot). You place that assembly underneath the visor and wrap a gold wire (probably 20 gauge & low Karat) around the element. with everything sealed airtight in the chamber, you then fire up the vacuum and once a sufficent one has been reached you then power on the lighting element. It should get hot enough to melt the gold wire onto the element and eventually it will evaporate off of the element due to it being in a vacuum environment. It will coat everything within the chamber including the walls of the chamber itself and will be permanently adhered to the visor, but it should be thin enough that you can still see through it.
They use this process to mirror coat sunglasses lenses, space suit visors, motorcycle visors, anti-reflective coatings on binoculars and camera lenses, etc. It's a relatively easy process to do but it requires a basic knowledge of vacuum physics and metallurgy. Basically any metal of sufficient medium melting point can be used to do this process (i.e.: gold, silver, aluminum, nickel); bronze, brass, & copper are also possibilities but will likely not work well due to their higher melting points and the vacuum draw not being high enough; copper also poses a surface tension issue which also makes it hard to cast. Titanium, tungsten, & niobium will not work due to their incredibly high melting points. Pewter & bismuth may pose some interesting possibilities but also may not work due to their incredibly low melting temperatures (around the combustion point of paper for pewter and just over 500°F for bismuth) and their virtual impossibility to find in wire form. Try to stick to metals that melt (and therefore will evaporate) between 1050°F and 2000°F.
