This Brainstorm process is a modification of the spatial smoothing script, making it work on a local scout
To make it work, put the .m file in your .brainstorm/process folder. In Brainstorm, put a source space file in the process box. Under Run -> Cogwheel -> Sources, you should find a new process called "Local smoothing". Select it. Follow the instructions on screen. Your smoothed map should appear in the same results folder as your input.
Please let me know through GitHub if it doesn't work. We can figure this out together.