Rather than paint, you might want to try Plasti-Dip. A lot of people are using it to coat parts of, or even whole vehicles. One nice thing about it is that you can simply peel it off if you don't like it. It should be perfect for mirror shrouds since they don't get handled a lot:
From what I understand, proper prep is essential. I did read somewhere that it lasts three or so years, so it's not forever, but it's not expensive and easy to re-do when necessary.
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Bob C
2002 Itasca Suncruiser 35U
Workhorse Chassis
If these are the plastic mirrors oh, there may be another choice. Those of us in the Jeep clubs I've become addicted to Meguiars Back to Black. For less than ten bucks it takes all the plastic pieces on the Jeep, which includes fenders and bumpers, and turns the black again. I use it on my motorhome mirrors and trim pieces.
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Minnie Winnie 26A, 2018
San Diego, CA
TOAD 2010 Jeep Wrangler