I use the cream cleaner for pvc by eurocell - it's probably the same liquid as loads of companies supply - maybe you could brush that on - at moment I do all this off a ladder but gonna try a suggestion one of the other wc's made - pressure washer with long lance - if you haven't done the pvc before, it's worth knowing that they don't always return to original look - I tell the customer in advance and they seem fine with that
good luck