There is a technique to it,.. and if you don't get it right the results will be unpredictable.
The learning curve is steep,... the best thing to do is offer another wfp'er a day's free labour in exchange for some on the job learning.
If that's not possible, search here for any thread about "technique", "frames", "vents", "Top frames" and have a really good read.
My advice would be to always be aware of potential drips. Vents are trouble, as are 2 top openers above 1 large lower pane. If you wash the top frame or vents it will take a few minutes for the water to stop dripping.
I personally avoid the top frame after the first clean, and find this really helps.