I cleaned my own windows the other day. Results were perfect (trad).
I am, however, just a few miles from the Atlantic, and afte the high winds we experienced here recently, many of my customers' windows have been minging.
This week I have found it just about the hardest going ever to get them clean. I even had a call back from one customer, and it took two more cleans to get them right.
The salt seems to stick like glue, and I have found that using a damp cloth to wipe the glass before washing, plus using hot water, has solved this problem.
John