If ur doing the roof too, I would try hosing it with tap water to get the thick off, then wfp the lot. If it doesn't come clean,then I would be recommending they contact a cleaning company that specialise in fire and flood restoration work, as doing the lot trad and cleaning the frame work with a damp cloth then polishing with a dry 1will take ages and you may undercharge ,unless they agree to an hourly rate b4 hand.