I found an intriguing video on how to use blend if as if it was a mask...
At first I thought I was already doing it but this guys takes it to another level.
Link to video
Actually, thinking of it...
This only gives a visual clue as to where the effect will be applied.
I also never thought to apply a layer from one image to another . So something new I learned from this video. That can speed up a process when working with a series of images with little variation in luminosity.
Clone brushes, blend being one of many, are not explored enough by us who do editing. That was my first thought and is a valid statement... However what you are talking about, now that I have watched the referenced video, is an entirly different subject.
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