One more option…
If you check out some of the local marine supply stores, you can probably find some fairing compound. It’s used for patching divots in boat hulls and the better stuff comes as a two parts system. It may be pricy, but it works well. When mixed together it forms into the consistency of really stiff peanut butter. If you use the right spatula to apply it, it’s amazing how smooth you can make the finish. Hardly any sanding is required. Before you apply it, you could grind out a nickel sized area around each hole, about a 1/16 inch deep. This will provide more surface area for the fairing compound to bite into. The marine stores may have other options as well, such as two part epoxies that you can add different kinds of thickeners to make your own fairing compound (but it usually doesn’t smooth out as well as the real stuff).. The local body shop supply store can sell you a sanding board that is about 3 X 14 ( can’t remember the exact dimensions). One of these hand powered boards makes it easier to sand the surface completely flat.
