My wife always has one of those disposable dehumidifiers in her car, (Pug 207 HDI). I used to laugh at her but, it does remove some amount of moisture from the interior and it doesn't cost a fortune.
I've tried RainX anti-fog product and it's useless. Tbf is does the job but leaves circle marks where you applied it like drawing on a bathroom mirror after a hot shower. For what it's worth RainX is sh1t too
I use those screen covers that costco sell on my Peugeot. Brilliant product and actually works, screen us clear. It's held on using elasticated straps on the wing mirrors, not tried it on the audi though
Tbh, the only thing that ever came close to working in my Arai was a Foggy mask. Anything else was used once and chucked.