Here is a little surprise I thought was so cool I needed to share it (and therefore, file it away for future reference).
I was designing and illustrating a children's place mat. There was an area I wanted to knockout with soft white. I took this art from Illustrator to Photoshop because I needed to apply some random texture to the blue. I wanted the white edge to be extremely soft, but I was getting a strange pattern.
While the pattern looked fun, it wasn't what I wanted for this instance. I wanted it to be soft. I used the smudge tool, but the pattern kept moving with the cursor instead of softening like I expected.
Finally, I looked at the layer. I discovered I must have put the layer blending mode on "Vivid Light."
When I set the blending mode to normal, voila! i got the soft borders back.
I'd encourage you to try all sorts of combinations with blending modes in Photoshop. You just never know what effect it will produce.
By the way, here is what the place mat looks at this point. This is a project for Warner Press and they own the copyright.