We used West System microballoons, so easy to use, sand easily, very light weight and are amazingly strong. The big surprise of the finish was the paint, used Interlux Topsider one part paint with much more success than we thought we'd have. I planned to put a rough finish on her before the trip due to the short build time, and then do a "proper" job after, but I am so pleased with the paint I wouldn't change it even if someone else paid for it! On the trip we had a few scrapes (you should see the van we destroyed to get our minor scrape) and they painted out very easily. Not cheap, about 30$ a quart.
We had her in the driveway for the last week and it was so nice to go back and finish some of the jobs that no one will ever see or care about, but that retirement allows me to do. My Grandchildren may appreciate the effort someday.
Have you seen the method of applying microballoons with a toothed trowel, then sanding off the high points, then filling in the "valleys" with more fairing compound with a flat trowel? Works great. My boy faired and painted the entire truck with no previous experience using that method.
