I sanded it smooth, which removed most of the mud, but the gap is filled and glass goes across the top of it. And it is smooth to the touch-n-feal. I'm going to wait untip painting time to work this glass stuff any further. I used 60 grip to take down the mud and glass until smooth, then finished it with 100 grit to take out scratches and make it smooth.
While I was at it, I filled in some riveting marks that were on along the trailing edge of the rudder on one side. I'm hoping this will improve cosmetic look when painted.