it helps to have a good razor plane. Not a cheap one. Your brother may have a small plane that would serve. If it's properly lapped and sharpened, you should be able to snick a transparent wafer of balsa from any piece of balsa wood, even end grain. I find using a plane is more precise than sanding, and minimizes dust. You only have to sand the final bit.

Also, make cutting and shaping templates from lite-ply from the hardware store (1/8" or 2.5 mm). It's cheap.

Good luck, and have fun.