RE: Dents and dings from building
One of the last things I do before covering an airframe is take a Q-tip and soak up a bit of water with it. Apply it to each little "ding" and bit of hanger rash and then use a hot trim iron run over the moist area to quickly raise the woodgrain. Do this over small areas at a time. Then go over the entire airframe with 320 grit sandpaper on a foam pad to remove the raised grain prior to covering. Using the Q-tip keeps the water in small concentrated areas and the heat does the rest.
Soft landings,
Joe