Exclamation mark feathering menu

[Ofnuts]

Exclamation Mark? Red triangle? I don't remember seeing anything like this in Gimp?  (screenshots?)?

Me, I would be very suspicious of a tutorial that:

• uses a large brush to fill a selection (instead of using the bucket-fill)
  
• uses the freehand selector for such a complex selection (note the acceleration...). The scissors are likely a better tool in this case. The Path tool would be even better.
  

Also, this doesn't give the look of a "shallow depth of field", this gives the look of a girl put over a blurred picture, because in a real picture with shallow depth of field, the part of the wall where she sits would be in focus, and therefore sharp, and would blur progressively as the distance from the subject increases.

Basically, for this kind of effect:

• duplicate the layer
  
• blur the top layer
  
• make the top layer as transparent as you want the picture to be sharp.This is the difficult part. The only good point of the tutorial is that it uses a layer mask for this. But if you are goint to paint over all the imperfections of the selection, then you don't need the selection. This also allows you to paint with a gray gradient the areas where you want a progressive blur.
  

Otherwise, Gimp has a "focus blur" plugin: you define a "distance map" on a layer and it does the rest.