I bought a bottle of Solution Finish at my local auto detail shop, and thought it worked great. Shop owner said on a daily driver he would have to apply it about every 6 months, so I expect it will last longer since my 914 is in the garage most of the time. I used it on the top, sail panels, bumper tops and front spoiler. You definitely want to wear rubber gloves when applying! Here it is on Amazon:

https://www.amazon.com/Solution-Finish-Blac...r/dp/B006NZRAFE

Some before/after pics:

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