If you work with balsa and plywood, you will fall in love with these sanding tools. They aren't cheap but last forever. Clean up with acetone and a blow torch and wire brush and they are brand new ready to do it again and again.
http://shopbvmjets.com/zencart/index...ex&cPath=65_69
http://shopbvmjets.com/zencart/index...ex&cPath=65_68
http://shopbvmjets.com/zencart/index...ex&cPath=65_67