Polish at right angle to the scratch, or you just might polish the scratch deeper.
You might put a belly in the surface if you remove material chasing the scratch.
An even mirror finish is difficult to achieve, and until the scratch is completely gone, a mirror finish will only add contrast, and might make the scratch appear black. Pahoo isn't far off with taking out the scratch with scotch green pad to a satin finish, and then buff. I have a PPK that i got for half price because of a very scratched finish, like you would get from carrying the piece naked in the pocket with your keys. The pad cleaned it up in a jiffy, and it looked so good in satin, I left it like that. The deal is if I scratch it the green pad takes it right out.