Masking/fixing Non-Clear coat Scratch?

[bagusbagus]

Have a large scratch across the whole door ( Keyed in ) on a newly acquired car.
The scratch is Deep & not a clear coat scratch , I have polished out /sanded most of the other scratches on the car with a good result.
However this one sticks out like a sore thumb, I do not have a budget to repaint the door.
Tried 1500/3000 sandpaper on it + DA + Pastes , Made it a bit better but it still is nasty..

I got a touchup paint however I think trying to touchup a scratch across the whole door is only going to make it look worse?
Goal would be to make it look less visible/mask it , currently it looks totally white on a red car.. so it's really visible.
Thinking how I could perhaps fill it in with something so its not white anymore and won't stand out as much?

[bagusbagus]

https://www.youtube.com/watch?v=S2aC_oseMe4

Here's more or less my situation.. even that pro dude could barely make it better.

[paintman]

Likely the white is the undercoat & you aren't going to make that red no matter how much polishing you do.
If you continue trying to sand & polish you are suddenly going to find that the panel is starting to look pink as you remove more red paint & the primer starts to peep through.

If a door paint is out of the question - and there is the the likelihood that without blending into the adjacent panels the painted panel will look different from its neighbours - you might as well follow the instructions in the video & see what happens as you really have nothing to lose.