ORIGINAL: Steve Steinbring
Take a little time using your sealing iron and a damp cloth to steam out most of the dings before covering. This method works well with dinged furniture, gun stocks, and other sorted wood items. A good deal of small dings can be removed by light ironing over the area even after its covered.
I do this alot as well, but I use a 50% mix of denatured alcohol and water in a spray bottle the mix puffs up the balsa and alot of the dings just dissappear, no heat.
for filling I like the Minwax Stainable wood filler its a bit harder than ordinary spackle and sticks to the wood very well, I do add a little water to loosen it up a bit so it spreads easyer.