After the mirror has had time to cure you should carefully remove it from the bag. At this stage small resin creases and stray fibers are normal. Using a razor you can easily trim the mirror cover to its exact final shape. Using progressively finer sandpaper remove any excess resin using care not to cut into the carbon fiber. Should you have any air pockets or low spots you will need to brush on another thin coat of resin much like you would paint. Allow the resin to cure and then carefully repeat the sanding steps.