I am having issues when trying to remove non cortical tissue (mostly skull). 

I load my images as follow:

freeview -v mri/T1.mgz mri/brainmask.mgz -f surf/lh.white:edgecolor=yellow surf/lh.pial:edgecolor=red surf/rh.white:edgecolor=yellow surf/rh.pial:edgecolor=r

Then I have tried to follow the guide in the tutorial 'Correcting Pial Surfaces'

Selected Recon edit free hand option, selected brain mask.mgz hold down the Shift key and left click. This does not change the surface.

I am wondering if there is a different key shortcut with O SX. Or if there is anything else I could try. I also tried older instructions with tkmedik and I have the same problem.

Any advice will be greatly appreciated.

Thanks,
Pablo