There is a sort of "reverse the image" type of one-click image filtering that makes ALL image flaws super-visible..perhaps one of TPF's knowledgeable members will provide us with details?
Can't say I'm knowledgeable, but I stayed at Holiday Inn Express once. Are you talking about the Visualize Spots feature in the Camera Raw filter???
With an image open in Ps, choose Filter > Camera Raw Filter. Select the Spot Removal tool from the toolbar, and then down at the bottom of the dialog box on the tool select the "Visualize Spots" checkbox. The image will be converted to B&W and inverted, with only the outlines of the image's elements visible. Use the Visualize Spots slider to vary the contrast threshold of the inverted image. By moving the slider at the bottom of the dialog box left or right you can vary the contrast levels to make the imperfections more visible. Hover the spot removal tool over the imperfection and click. When you're done uncheck the "Visualize Spots" Checkbox.