Experience, like Darran has said, shows there is no 'right way' to clean cladding, it may well be a combination approach.
Unless you are really lucky pressure washing won't touch any discolouration weathered into the cladding, the photos above are only a very small part of Sainsbury's Darlington works.
Pressure washer has not been switched on.
The TFR chemical used can often be hit & miss, depending on which one you use, fairy washing up liquid applied and then agitated is as good as anything else but chemicals will need to be scrubbed in.
Because of the vinyl residue this had to be hands on and couldn't have been done off the ground, even without it cleaning cladding at the same height as yours - NO - save your shoulders.