Building techniques
Brett,
I only use sand paper. The final two stages of sanding should be with 400 grit followed with 600 grit. Both of these should be used only after all small imperfections and pin holes have been filled and sanded.
Prior to covering, I vacuum up as much of the balsa dust as possible, then wipe a tack rag across everything.
This will produce a very smooth surface without adding weight.
It's a lot of sanding and a lot of prep work, but the finish is superb.
ED