The Create Alpha button provides the BlurMask operation, though blurring current mask for later use no texture is on the already fully masked.
The Intensity Value slider determines the intensity of future masks applied to the selected SubTool. The options can be selected however you want, either on their own or together. Also, while holding the Ctrl key, you can apply the current Alpha as a mask by clicking and dragging from outside the object.
does need to be dynameshed in
mask multiple zbrush
free for 7 32 bit full version
pro trial version download