How to mask out brush in After effects I've run into a little snag.
I can't seem to mask out some of the brush that I've used on a an empty layer.

I create the mask but it simply doesn't mask out anything, it does however mask out pixels when I did some experiments.

How can i get this done?

Thanks!
Create a white solid, mask out what you want with that...then use it as an alpha matte to mask out what you do not want.