Perhaps I'm just being dense but I'm not finding the solution to this supposedly easy process. I've done this dozens of times in Premiere, After Effects, etc.

How do I mask part of a video track to reveal a video track below it?

I've tried the greyscale mask parented over a child video track but all I get is the child video track revealed through the white of the mask and black in the black areas of the mask. I want to see the second non-child video track through the black of the mask.

Thoughts?

Michael