i am almost finished with my EOD helmet and am wondering what is the best material to use for the visors and how do i cut it and actually attach it to the helmet
The best material that (most members have found) works is a reflective motorcycle helmet. For an Halo 3 EOD helmet however, you can simply use some cheap sunglasses lenses that are polarized.
This is the visor that I got from Amazon. A little pricey but worth it. There are better ways to cut it and mount it than I did. I suggest you visit Carpathias build. He is very good at mounting and I am sure you could find a great way to mount the visor in there. Good luck!
depending on the color you want, if the EOD helm visor is small enough you may be able to use reflective tinted sunglasses and glue the lenses into place