I'm preparing the surface for sealing. This involves a light sanding. Dents in the balsa can be removed by dampening the area with water. This raises the grain of the wood and eliminates most dents. Sand when dry.
The most common method of sealing balsa is with AquaNet hairspray. Yep, hairspray. I prefer Deft Sanding Sealer. It adds very little weight and must be brushed on. Dries quickly and sands easily. I use it sparingly, wiping off the excess as I go. When dry, I re-sand the surface.
Surface prep and sealing will probably take a couple days. I work slowly.