In my opinion the use of pressure washers are not ideal with the likes of an x-jet for softwashing vertical surfaces like render walls etc as can create far too much chemical drift.
Best practice now seems to be using a wfp either with a spray tip or wfp brush attached so can spray close/directly to the surface so reduces the amount of chems used and overspray/drift dramaticaly unlike using an pw x-jet spraying chems upwards from the ground.