The method I just posted does not despill directly. It gives you the amount of green that despilling would remove from the image. You could set this layer to "Subtract" to remove that green from the original image.
Also I wouldn't use the Darker Color blend mode for despill. Darker Color works based on the luminance of the pixel where as Darken works on a per channel basis. The results generally won't be any different (unless you've modified the R/B channels as well) but I consider Darken to be best practice.