Hey mate. Definitely avoiding using paint polish on your rubber seals. It'll just make them far worse!
It's only natural for real rubber to fade and dry out. You need to "feed" and protect it to keep it fresh looking and feeling.
Since I got my Golf R six months ago, I've been using 303 Aerospace Protectant. I used to use an old Meguiars product in a red bottle on previous cars, but it seemed to only keep rubber moisturised for a few weeks or until it rained. Now I just use the 303 every other month after I've washed and dried my car.
It comes in a spray bottle, and can be used on so many things, including throughout the interior - pretty much everything which isn't cloth/carpet/glass, although I use a dedicated leather cleaner. You could also use it on your tyres, but I don't think it's a cost effective solution for that compared to some other dedicated tyre dressings.
On the door/window seals, since they're relatively thin and don't give a "wide area" condusive to spraying product on, I instead spray the 303 onto an absorbent paper towel, and then wipe the towel along the seals to spread the 303. Whilst you don't want it dripping off, you want to apply enough that it takes a few mins to soak into the rubber. Then after 5 mins just give them another wipe over with a clean paper towel to ensure any remaining product is cleaned off.
I'm very happy with it!
Whilst I've only been using it for six months, if you do a search for it on these forums, you'll find there are lots of happy campers using it - some for many years.
Hope that helps.
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