Full-Face Helmet Anti-Fog Advice

I have a Shoei full-face.

I've noticed that on rainy days and in cold weather the visor fogs up. The
vents don't help a lot. I have to open the visor slightly to get enough
airflow. On rainy days, no big deal. But on cold days ... it is cold.

Are there any other approaches? For example, are there coatings or special
ways of washing the visor that will help?

Thanks.
--
David T. Ashley (dta@e3ft.com)
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