I'm sure they probably have some filter or tool built in that works better, but a simple way to do it in Graphic Converter is to do a Save As for the file, make it a jpeg, and then lower the quality as low as it will go (or relatively low...whatever it takes to blur the stuff) after pressesing the Options button. Then open your blurred file, copy the blurred section that you want out of the file, paste it into the original picture, and put it over the right spot. It might be a bit ugly, but it gets the job done.