>>> Wish I could do that for Normal map creation but I've not found a way to that so I just use the created Bump map to make the Normal map.  That works pretty good!  

The Green channel of a normal map controls the direction it faces. For example, if you find that a normal map is saved in DirectX format, you can invert the Green channel to make it OpenGL format, and vice versa.

So, select the area you want to invert and feather the mask.

With the selecttion still selected, switch to the Channels tab in the layer manager. Select the Green channel, and press Ctrl+I (for Invert). Or choose Image > Adjustments > Invert.

The innie becomes an outie.

Top is before inversion, bottom is after inversion.