You can always use usual cleaning tools like Clone Stamp and Healing Brush. However for product photography I like to use Photoshop Filters and Masking. Let me show how I do it? Below you can find the simple steps:
1. Open the image and Duplicate Layer
This is 100% crop of the cosmetic brush image
2. Go to Filter/Noise/Median…
For this particular image I’ve choose radius 13. But you drug the slider until all small dust disappear.
3. Filter/Noise/Add Noise(Gaussian, Monochromatic)
4. Filter/Blur/Gaussian Blur
Median 13, Noise 1.5, Gaussian Blur 0.5
5. Create Hidden Mask Layer → Layer Mask → Hide All and paint over the object to clean dust and even borders. Do not paint all object, only areas you want to clean.
This is the final result:
This is another example:
Median 9, Noise 0.7%, Blur 0.5
Try it! It’s really fast and easy:-)