[Freesurfer] White Matter Edits vs. Control Points, & third party software

I have some questions about how to manually correct the white matter regions .

It's the same manually edit the volume "brainmask.mgz" and use control points? Would I get the same result? My intention is not to use control points, but directly replace the voxels that have not been classified as white matter with the value 110. Is it right to do this?

My second question is: Is it possible to edit the volumes with a third party program? My intention here is to turn the volume "brainmask.mgz" to " brainmask.nii" using "mri_convert" command. Then edit the values of the voxels manually with a third party software or painting tool, and finally, turn the volume back to "brainmask.mgz", replace the file in their respective directory, and finally execute "-autorecon2- wm". Is it right to do this? Or this may compromise my data?

Thanks in advance, Alberto.