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The "dust" will be dense most especially in darker areas.  I think I lowered the opacity to 35%. At 50 its more denser.  When in the Noise filter callout, you'll see that some areas in the preview are dense than others. It may need trial and error to get the amount you want but maybe you'll be satisfied on the first try.....

Hope this works for you. Post the result......

btw.... to get the dust grains sized to match your sample image, I had to resize up the noise layer. I dunno if this will look good on what you'll be doing but give it a try as well.