Strangely enough, HD wax is what I use on mine, as well as the Harley.
Am hitting my S8 with the 1500, 2500 then 3000 grit then buffing before re-applying the wax, I'm quite pleased with the panels I've attacked so far, not well or fit enough to do the whole car at once unfortunately, but didn't realise that Audi Aluminium Silver (L7YM) could have such a deep shine after 14 years
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I Love the smell of petrol in the morning!
Other vehicles
1968 Rover P5B Coupe (Modified & V-Quick, but I have to sell this now

... Boo Hoo!)
'92 Mitsubishi Pajero V6 (Petrol) Super Exceed (Gone now)
'06 Harley Davidson Night Train
Oh Yes....... The '98 PF S8!