Blur Brush for manual painting of textures and masks

A brush that blurs brush strokes. Its called “smooth” in blender and Zbrush.

Justification

Its an essential tool when handpainting textures or masks, especially for more stylized textures.
You could use a blur filter in some cases I guess, but it might be easier for quick fixing of paint strokes and more convenient for those less technical artists, that just do it all by hand.

Implementation Details

Ideally this would not be a separate brush, but rather a brush modifier you could access for example by pressing “shift” or another key, or you´d have to switch it like you can switch between "paint " and “erase” with B and E

EDIT
I did some further testing and blurring by using a filter unfortunately is not a workaround right now, as it doesn´t blur across UV tiles. So, if you paint across UV tiles, the blurred paint gets “split” at the seams.

If its possible to circumvent that behaviour for the filters somehow, maybe an implementation via a blur filter rather than a blur brush could be an interesting option.
in my trials the updating of the blur filter was pretty instant, when adding paintstrokes.

Thanks @insertmesh for the feature request and for doing some additional testing!