There is a reason why I laugh at the idiots who "Dip" their entire cars. You can never polish/clay any contaminates out. Once dirt/dust/grime start to ingrain themselves, it looks like shit even more than when freshly painted!
As for being 'un-doable'. Yeah, if you have an extra 30 hours on your hands to get every speck of the residue out of all of the seams after!