The texture on the stock mirrors is pretty thick so I'd recommend heavily covering the glass w/ tape and paper and possibly removing the chrome caps or heavily covering those, too. They are raised slightly above the mirrors so they'll get in the way of sanding. I can't remember the grits off hand but they are a bit time consuming to fully sand down b/c of the shape and what not.
I just thought of something, I have a set of fully painted stock gray mirrors. They aren't really that smoothed as far as the texture but they are smooth to the touch w/ the paint. They were professionally done but you'd probably want to sand them down and paint them again. In perfect condition but still have that texture look from up close. I didn't specify to the body shop that I actually wanted them completely smoothed first, they thought I wanted the factory look w/ paint ...don't know why.
Just thinking, if you're interested we could trade (mine + some money) and you could swap the guts of yours into mine. They are manuals and one piece (no cap/cover.) I have pics if you want them, let me know.
