I am building my own pen from various lumber that i have access to and am close to being done (hopefully ). Since it is made out of wood, i am wanting to treat it to protect it from the elements. What would work well but be safe for my birds? I know they can be sensitive to chemicals. I've seen someone recommend Thompsons water seal. I need something along those lines because I'm wanting something i can paint (or spray) on the whole thing. Will that work and be safe, or is there something better?