Cleaning dust and scratches from scanned slides.

One of my favorite ways to eliminate dust was to use dust and scratches on a separate layer. Make it the setting eliminate the dust, but bring back the grain. This will mess up the images fine detail. So add a black mask to the dust and scratches layer, then,  with a white brush, paint away the dust, being careful to avoid the fine detail areas.

If you go back enough years you may recall a technique for getting rid of dust and small scratches that involved the use of the History Panel and the History Brush Tool. The process takes longer to describe than to do. 

1.   Cmd+J to make a duplicate layer
2.   Filter > Blur > Gaussian Blur. Move the slider slowly until the dust disappears.
3. Choose the History Panel and move the History Brush symbol to the bottom step: the one that reads Gaussian Blur.
4. Choose the step directly above it. All the blemishes will reappear.
5. In the Tools panel choose the History Brush. 
6. Adjust the History Brush size and tap on each blemish or close group of blemishes. Don't drag it across large areas. It will blur the image.
7. Flatten the file.

I believe you are referring to the Spot Healing Brush. After adjusting the brush size (via keyboard square brackets), click on the dust spot or small scratch. 

Hi if you post your image here we can guide you easily...regards