Specifically, I put the luma key on the video in V2. Then, stepping into that effect, I put the grayscale image into the layer below.
Then I applied the BCC Make Alpha effect to the grayscale image and set the output to a gel.
I thought that the resulting crisp image would make it easier for the luma key to work. (The gel output sends out a black and white image with a gray haze only where the change was occuring. This black and white image changed over time.)
It kinda worked but during the duration of the effect, there was either a black or white