If its deep its fucked! buy a new one.
If its not so deep you can polish them out but it is hard work in the long run its easier to just buy a new one.

Unless you wanna be there polishing a visor all day.
Myself I would rather pay the price get a new visor and then ride all day.

Get a new visor.
I did the same and tried to buff it out.
Have to buy a new one as now have an annoying smudgey bit and no scratch.
Always happens at your eye line.

Brasso is good for somethings but  if you have it try it and if it doesn't work buy a new one.

"Mothers plastic polish" is good for shallow scratches. I bought a screen which had been marked down because of a scratch, and managed to polish it out with the stuff. I didn't expect to get a good result, but it worked well.

Gonzo.