i have to clean some window frames that are powder coated metal i have tried fairy liquid , a strong degreaser and another cleaner which i use on upvc with all the colour of the frames return to a very dull finish , i noticed around the door where peoples hands grab the door to open it the finish is the darker original colour (grease body oil) from hands so tried WD-40 on a small area which seemed to work !! my question is has anyone else ever done this? used WD-40? or know of a better product method ? many thanks in advance