GIMP :: Working Of Blur Tool

The blur tool does not seem to be working like I thought it would work. I am using version 2.8.4.

When blurring a section of a digital painting or photo, it goes to a certain point and then does not seem to blur anymore regardless of how much I keep painting over the area with the tool.

When I apply a gaussian blur filter to the entire image, I can get much more blur to occur by choosing a large blur radius.

I would think my continuous painting with the blur tool would be the same as choosing larger fill radii in the gaussian blur filter. But, as I said the tool stops blurring anymore after a few strokes over an area.

I have tried changing all the different settings - Rate=100, Opacity=100, change the size and style of brush, etc.

I have a created a workaround for the problem by doing something similar to the trick for sharpening that is mentioned in the Blur Tool documentation:

-Duplicate the image layer a few times.
-Go to the duplicate layers and apply different levels of blur.
-Choose the Clone Tool.
-Select 'Image' and 'Registered' from the Clone Tool's control window.
-Activate the Clone Tool on the layer that has the amount of blur desired.
-Switch to the original layer and begin painting the blur with Opacity set to about 60 and use brush dynamics where pressure controls opacity.

This seems to work okay. But, it is a lot of extra steps to get the blur to go further than the Blur Tool allows.

It would be nice to have a blur radius setting in the Blur Tool's control window. Could that work?