I think mirrors are one of the few bits on a car for DIY refinishing. They are a small area, and don't touch the rest of the car, making the colour match less critical.
As it's just the covers that are body colour, it makes sense to remove them rather than mask the whole mirror. Then you can mount them on a stand to actually paint them. That sounds grander than it is; some scrap bits of wood, masking tape and ingenuity will do the job.
An aerosol should be enough to do both; it certainly was for my mother's Focus.
If the existing finish is OK, then a quick scuff with scotchbrite and degreasing should be enough prep.
Several light coats at 90 degrees to each other until you have a nice even colour. Or run out of paint!
Then I use 2pack clear lacquer from a gun to finish. This is the real key to a decent, lasting job. I did the Focus ones about 4years ago, changing them from blue to red, in about an hour one evening. They're still good.
I'm happy to help