Good to see it can be applied in other software. (I used PSP back at version 4, but that was a while ago )
One other bit is to play with the curves dialog before blending the images. That will let you do things like the attached - and island ringed by a reef. (FYI - I just started with a blurry blob but used the curves adjustment to make the "ring" appear. I can grab the curves dialog if anyone wants, to show what I mean...)
-Rob A>