When I peel the entire seal off the top of a new vanilla bottle, I leave the seal intact. To control how much vanilla pours out of the bottle, I just poke a little slit in the seal at the top. When I add vanilla to something, I just squeeze the bottle and it comes out in a little stream.
(Yes, this is imitation vanilla. So sue me.)
(And true, you can never have too much vanilla. Save some for the next batch...)