Vinegar works better than either bleach or ammonia. Remember the chicken leg bones you softened in science glass as a child? Use a small spray bottle to dampen (not soak) the side that will be the outside of the curve.

AAA balsa is simply one manufacturer's way of convincing you their balsa is best. LOL! AAA balsa will possibly be cut more accurately, and will not have any grain defects. Don't be ffraid to make the hobby shop manager mad by sitting down on the floor and going through every piece of whatever size balsa you need until you find just the right piece. For the price they charge in hobby shops, you can do this.