anyone got a fool proof wfp cleaning method ? NO
but has anyone got a fool proof trad method ever, whether you are trad or WFP you will leave spots or smears depending on what tool you use....
What I say to the customer is if there is a problem then I will come back and redo it...
If you are noticing more spoting then your windows have probably always spoted and with the days staying lighter longer you can see them :

it could be user error or a problem window
at least if it is a problem window and causing spotting your window is not going to be trashed by the rain if done trad
