Trad and wfp both use the same principles. Break down what's on the glass and then remove it. Trad, you wash the glass, break the dirt down and then blade it away. Wfp, you scrub with the brush to break the dirt down and then rinse it away.
It's that simple.
But in practice it's not because we all want to get on to the next window. If there's no dirt left on the window and all your gear is sound then you
should have no problems, generally.
In Johnny's case and the problems most tradders have, in my experience, is in the soaping up and not the blading, I reckon.
They don't do enough and end up with lines, kicks and smears as the dirt left is squeegeed around. If a window is dirty, keep washing it until you think all the dirt is gone. Then wash it again another 2 or 3 times!

John, microfibre the window BEFORE soaping up. As an experiment, target areas of six square inches, say, and wipe and wipe and wipe. Then soap up- with enough water- and and there should be no problems.
It's the same with wfp.
But I'm not as good at wfp
