Look, the whole reason K-9 units even EXIST is to create the probable cause. If the dog begins to smell something, even with the doors closed (which they can do), then that counts as probable cause. That is the whole point of their existence.
What happened in that video was that the poice officer did not want to waste his time calling in a K-9 unit on a hunch so he just wrote a speeding ticket.
What you folks REALLY have to remember, though, is that in the courts, it is your word against the cop's. The judge will almost always side with the cop. If a cop says he "smelled something funny" but really didn't, all he would have to do is force himself in there. It is VERY ILLEGAL to use ANY physical force against a cop. If one wanted to get into your vehicle badly enough, he would.
Now, the trick is to not let him think that he should waste his time searching you. Whenever I go to smoke, I usually dress as far away from the "stoner look" as possible. Suits w/ ties, jock clothing... anything to make that cop think that searching you would only be a waste of his time.
And smoking in the car is the stupidest thing you could do. There are NO contingencies if a cop feels like being a dick. And some do.