like they said get the builders back, but the custy might not want that, i would charge her a hourly rate and just take my time and clean them all up, just explain to the custy that u dont know how long it might take as plaster could take 5 mins a windows or an hour a window all depends how it comes off. i would then price it in to ur regualr price after the first clean, at least the hard work will be done then