Visors are actually only about 30-35 bucks seperately, but if you want to do the double layered effect, you would need 2. I've heard of people using coke bottles and stuff and just layering gold tint on it.
A Glaze coat is basically something to further smooth out your armor. From my understanding, it should be done last, and requires minimal sanding.
Bondo(body filler) is similar to glaze in that it's something that you put on to smooth out your armor. However, Bondo is used for details and usually leaves pinholes and such. That's what the glaze'll fill in. You usually do a light sanding on the outside, add bondo, and then sand that for smoothness. To my understanding, you'd put your glaze on after this.
It also depends what helm you have- if you're Slyfo's or Flying Squirrel's, you might not need bondo because that has most of the details on it to start. I think Spase only glazed his, and didn't use a lot if any bondo.