How to track glow effect on face?

Hi there,
in the music video of Carpenter Brut's

you can see a glowing cross on the forehead of a woman.

My simple question is: How do I attach this effect in Fusion to the forehead? In my experience, the results of trackers are not good enough to bent the cross shape in a proper way when the actress is turning her head.
Or do you just stick a green tape on the forehead of the actor and work with a keyer to exchange the green parts for a white background node followed by a glow node?

What will give me the best results here?

Thank you very much!

I just found a making off. Obviously they painted black crosses and used a keyer.

I'm a bit surprised they didn't use bright green or blue - something that is easier to key...

From the look of the rest, it might have been easier to key, but dealing with the spill would probably be more work than changing the black to bright.

Chroma keying works best when luminance across the chroma image is even, and the chroma color's luminance can be maintained. If you're putting the key source on someone's face that presumably you want to light attractively, a chroma color is far more likely to fail. In addition, paint that works well that way tends to dry stiff, which will reduce the actor's ability to emote. A black marker, though, doesn't need to receive extra light, and it won't impede the forehead's mobility. As long as you're not using chiaroscuro lighting, that black mark will probably be the darkest thing in the skin region. A little garbage masking to protect hair and eyebrows, and you'll be able to get a decent matte with the luma keyer. Then all you'll have to worry about is hair crossing the mark.

For something more involved, like if you wanted to track in a wound or a tattoo or something, you'd probably need an actual 3d track of the head.

Thank you very much, that really helped! I'm thinking about using a similar effect in my next music video.