Have used Rainx on all my cars for a couple of years and works great.
However they also make an anti-fog product for the inside which blows chunks.
The better half heard a claim that shaving cream works for stopping fog on bathroom mirrors
so tried it on the interior drivers half of my convertible XJ-S.
Went out on a very rainy/cold Northwest day (just about everyday) and it worked perfectly.
Drivers side was clear as a bell passenger side fogged to invisibility.
Something that’s cheap and works great, what a concept.!!
1991 Classic convertible XJ-S (no fog)
1976 Dodgey Van
1981 Subaru (death trap)