K2r spot lifter for clothing, carpets and upholstery does a great job of removing fuel from balsa. Just spray it on, let it dry completely, and brush/vacuum off. Repeat if necessary.

You should be able to find it at Wal-mart, most grocery stores, etc. If you can't locate it, call their help line at 1-800-787-6060 for a local retailer.

Lynn