Smooth Brush
Using the Smooth Brush tool will allow you to soften or blur edges. The Smooth Brush has the reverse effects of the Sharpen Brush tool.
To use this tool...
Choose the most convenient magnification level to work in and then click on the Smooth Brush button. Hold down the left mouse button and move the Smooth Brush by moving the mouse. The size, strength and style of the Smooth Brush can be modified by double-clicking on the Smooth Brush button.