I know that wasn't directed at me, but I thought I'd share what I know too..
Our first helmet used a Particle shield visor (kinda' like a riot face shield, but a LOT flimsier) that we tinted to the gold/orange color. On the first try, we inserted the visor from within the helmet.
It didn't look right, so I cut it down to re-apply it from the outside. Unfortunately, I used my Dremel and it's circular saw spinning blade attachment, very slowly and carefully.
The action of cutting the visor started to melt it because of the heat generated. Since the tint was on the inside surface of the plastic, you could see the plastic changing colors, seperating and crap where it kinda' burned it.
Later, I had better luck with a jigsaw, and no tinting. The key was to move fast and keep going. Then when I tinted it afterwards, there was no noticeable burns in the plastic.
We abandoned that design later and pull (vacuumform) our own visors now. Since we went with the "Globular" glass instead of the flat curved glass, we were unable to roll tint it though.