I did a builders clean today on a building site and noticed several scratches and bad stains on the window sills, :
I didn't notice them under all the dust and dirt, so I reported it to the site agent straight away, he came along and had a look,.... said no problem, we have the plastic Doctor on site???
(one of those upvc repair specialists) he phoned the guy, who was with me in less than five minutes.
Being interested, I asked him how he was going to remove these scratches, watch and learn, watch and learn he said.
He asked me for some soapy water, so I obliged, with this he produced some wet and Dry sandpaper (2000 grade) dipped it into the water and began to rub along the Length of the sill, within minutes all the scatches has dissapeared? and the sill was like new.
You must use 2000 grade with soapy water, and only rub in one direction and that is in the direction of the scratch.
Just a little tip I thought I would pass on in case anyone gets complaints about scratched sills caused by your brush.