I would agree that a dremel might be a bad idea but not the lighter method. I have used the lighter method on every mask I have had over the last few years and it works really good. Don't hold the lighter in any one spot for more than a few seconds and you are fine. Burn off the silicone then rinse, wipe and do it again until you don't see your masking fogging during the process. Here is the video I used to learn this method.
One thing to keep in mind, if your mask has any kind of polarizing coating inside the lense don't use abrasives. I boughta ScubaPro mask 3 years ago and did used abrasive toothpaste at the advice of my LDS and it scratched the crap out of it. They replaced it because they told to use that method. The newer ScubaPro masks have the polarizing inside the glass now from what I have heard.
[video=youtube;AxkqJqM6UTA]https://www.youtube.com/watch?v=AxkqJqM6UTA[/video]