Guy.. not all VW paint is hard
try the ones with no top coat
like mine.. marks by just looking at it. i have to be very carefull by the ways in which i clean it, y'know like pat dry bla bla bla
iv done my full car, removed every single swirl and mark, with ZERO hologramming (im sure you know this is a big issue on black cars), i managed to remove all marks with a orange polishing pad and megs 83
tried the same on bens flash red mk3 and the same sort of marks would not shift, rock hard paint as you say. I jumped to a Yellow Hex pad and megs speed cut 95 which did the trick in no time. i couldnt be arsed to do all that with a DA.
but i always work panel at a time as you mention above, this is sound advice