Visor fogging up

[Rider]

So it was 50 when I left for work this morning and my visor kept fogging up pretty bad. I have a breath guard on my helmet, but it still fogs up. It seems to be getting worse because it didn't used to do it this bad.

Is there some product I can put inside my shield to eliminate the fogging? I don't want to hear any "I heard that.." or "My friend's cousin uses..." I want to hear first hand experiences what works.