I had a little idea to fake the blurfilter in Inkscape.
Create a circle with the ellipse-tool, (color what you like) . Now open the fill and stroke editor and click the radial fill button. Set the masteropacity to 10% .
Now the cool thing, painting like pixelsoftware:
Select the circle and start dragging the path over the canvas while the space key is pressed. Here is a short video how it works:
Have fun !