The key to the Dust and Scratches filter (Filter > Noise > Dust & Scratches)is that you want to keep the Radius as low as possible and the Threshold as high as possible.
I actually saw a video “the other day” about this filter, and found it very usefull and easy to use when repairing very old photographs i am scanning for preservation and webpublishing, 🙂
And go back and mask back in the things it thinks are scratches in digital images
Great suggestion Bryn! Otherwise you might loose important details like small catch lights etc.