As you know since you commented on it, I just did that on my Avalanche. Same process with the duplicolor in a spray can. I got the perfectly smooth finish - actually smoother than the factory. All you have to do is get some 2000 grit wet/dry sandpaper and wetsand them until the clearcoat is smooth. After I did that, I added 3 more coats of clear (not because I had to, but because mirrors face forward and tend to get hit by rocks) and then wetsanded again.
Once you have them wetsanded nice and smooth, all you have to do is use some wax or polish to get them to a high shine and they will stay that way. If you have a power polisher, it will take less than a minute per cap to polish them out. If not, it still only takes a couple of minutes.
If you take these couple of steps here, as long as you got all the texture off when you sanded them, you should have a very professional looking finish.
BUT, as they are, they already look much better than the crappy textured plastic they originally were. Good job.