I had to do paint correction on swirled oxidised water spotted dull paint this spring & am really happy with my results. I basically used griots complete coumpound & a porter cable dual action polisher for correction & then klasse all in one paint sealant topped with p21s carnuba wax. after that work when it gets dirty a little water & meguires car wash soap & it looks as good as the day I did all the work
Porsche paint can apparently be pretty tricky.
If your interested detail & before/after pics of my project can be found here
https://www.autogeekonline.net/forum/auto-detailing-101/108548-help-me-fix-my-black-2004-porsche-paint-pictures.html