There are lots of little cracks, but the biggest crack is 0.040". Can I skip the sawdust thing?
I put some water on it to see if it would swell up. How many days should I let it dry before doing any of the treatments?
Get some exterior grade paint and matching undercoat.
So just regular paint from the hardware store. No special marine paint? If I decide to leave the rudder in the water, will that be okay? I was thinking, if a wooden boat can be left in the water all the time, I could just use the same kind of paint and leave by rudder in as well.
edit2: I put the rudder in some water for a few hours and now all the cracks are gone. I would imagine painting would have the same effect.