There's a very large development near me where the window frames are (will try to explain ) low profile
and have two openers above the glass below.
The opener drain hole is supposed to let the water drain out onto the frame below which then has a drain hole
to let the water away without touching the lower glass.
Unfortunately they don't work, the water gathers in the gap between the opener frame and the frame below and it
then leaks out past the degraded rubber seals gathering dirt onto the window below.
Not joking they can do this for hours and will nearly always leave runs on the glass.
There is no technique in the world where you will get these right using wfp unless you want to spend all day
waiting for the drips to stop.
Get a few of these on your round and I guarantee you will have a totally different outlook to wfp.