To control how much glue I use and where it goes I often use a small paintbrush to "paint" the glue onto a joint.
I'm late to this thread, but I wanted to second this advice. I have done some amateur woodworking, and that's how the pro's do it. They'll use either a paint brush, or more often maybe a foam brush or squeegee. For covering small edges like the balsa ribs, it's sufficient to put a dot of glue on the brush and then slide the part along it. The key with wood glue is, "enough, but not too much". But "enough" is far less than most people think.
The other thing to do is, if you apply too much, wipe it off with a wet paper towel or something similar before it dries. When it is wet, it is easy to clean up. When it is dry, it is a real pain in the butt.