How do you create an animated mask for an image to show underlying video for v2.82a? EDIT

I'm using Blender's video editor to overlay an image on top of my video footage. The problem is, I need to mask (make transparent) certain parts of the image that are currently blocking part of the video at certain frames. I am able to create a single frame mask and apply it to an adjustment layer that works as exactly as intended by showing the underlying video. I was able to create an animated mask in the movie editor, but when I apply it to the adjustment layer the mask doesn't work at all. I compared the strip settings of both the single frame and animated masks and they are identical, both using Alpha Over as a blend mode. I followed this video tutorial (times 7:22 - 9:22) but the animated mask is still not masking at all. I'm not sure what I am doing wrong.
In the movie clip editor (not the sequencer) you can create and animate masks.

In the VSE select the strip you want to overlay, add a &quot;mask&quot; strip modifier and select the mask you want to use. Then set the strip to use &quot;alpha over&quot; blend mode in the Adjust-&gt;Compositng settings for the strip.
The top strip will be overlayed on the bottom strip using the mask as alpha channel.

There is no need to create black and white images to be used as masks. The mask tools for blender are quite sophisticated.