Wash wash wash, rinse rinse rinse.
Depends how big the place is to an extent. Give all the frames a damn good clean, particularly getting up in between the sash gash
. To achieve this turn the brush head round, so its upright and youre scrubbing the underside of the upper sash.
Do that on all of the windows. Go back and scrub again but rinse, thoroughly this time. Then go back and rinse again, this time keeping the brush off the lower sash profile and with a lower flow rate.
Next day call the custard to see how things are looking.