I know this isn’t exactly what you’re asking, but after trying different sprays, coatings, and cleaners to keep my mirror fog free, the most foolproof way to deal with fogging is to deal directly with the cause: the mirror surface is cooler than the surrounding hot humid air, leading to condensation. Running the mirror under shower water for 5-10 seconds to warm it up before shaving has never failed me.

Just thought I’d throw it out there since the anti-fog coatings eventually wear off.