I have brick paving to power wash, there are trees on one side and that's where moss would be the worst.. There is also dandy lions and weeds growing everywhere.. ( place just been neglected ) Is there any weed killer I can spray over? And would you do it before or after pressure washing / sanding? Or what way would you go about it? I don't want to do it and see dandy lions growing again in a month or 2 as I do his windows monthly.. It's for a guy who deals with credit card terminals and I asked him if he gets his driveway power washed I'll take a terminal..