This car has had multiple driver's side mirrors on it, and now has about 8 holes of different sizes in the general area where the mirror should go. How would y'all recommend repairing this? I'm thinking using brazing rod rather than welding, because it should be less distortion. I have a TIG and am reasonably decent at TIG brazing. I am, however, worried that it'll more or less sit on top of the steel so when I sand it down flush, the hole will still be there. But that could happen if I tig weld in filler rod too. Thoughts?

Maybe if I slightly dimpled each hole in, by like 1mm in a conic shape, the fill would have good enough depth to handle being sanded down.

I wouldn't bother with brazing or welding. Just dimple the holes and use filler ... either way don't forget to paint the back side of the holes inside the door

In the past I've used very thin sheet metal epoxied to the backside and then used filler on the front side and sanded it back.

Note this would be on race cars.

For a road car that I wanted to be perfect, I'd fit a new door skin or patch panel.