Adobe Lightroom 5 came out with a new feature called "Visualize Spots" that helps you to find dust. More information on the feature can be found here: Adobe Help
How can I achieve a similar function in Adobe Photoshop to find dust spots or similar imperfections? I sometimes am working on an image in Photoshop for more serious editing and don't want to import it into Lightroom just to perform this. I also prefer some of the healing tools in Photoshop over Lightroom so it might be more useful in those cases.
Here is an example image with quite a few spots in it: https://dl.dropboxusercontent.com/u/95761/church_dust.tif
For reference, here is what Lightroom 5 was able to find in the example image:
Attempt based on answers
Based on the two answers thus far, I tried two tests.
Original on the left, Matt Grum's in the middle, and Unapiedra's first solution on the right: