Some find Vince entertaining.
(But not everyone is entertained by a clown.)
And he does make the point of hitting through the ball that you mention, he just doesn't give much insight into how to do it.
You may be interested in hearing from a real student of the game, and a fine teacher - Pat Dougherty, the Bollettieri Camp "Serve Doctor".
Forehand Leverage, Contact Zone and Alignment to the Ball http://www.youtube.com/watch?v=SZqhHdmqSPQ
In the above forehand video he demonstates the great long contact point that you need, even with a pronounced low to high swing, and even with a windshield wiper motion.
(Vince mentions Fed's forehand as an example of hitting through the zone. He does, but so do all the pros, even though the "bent arm" forehand of Djoker, Murray, etc. predominates on the tour, as well as at you local courts.)
If you watched the Australian Open (or any match), you saw how even Fed hits most of his forehands with a pronounced low to high motion - but obviously he is moving the head of the racquet through a fairly long hitting zone as contact is made.
It's just that the head is moving so fast that on TV, or even in the rapid action photos of his forehand below, the human eye just can not see the real motion going on:
In the above photo sequences, only the middle one is where he flattens the ball out (the telltale sign is the racquet on follow through finishes only about shoulder height) going for a winner (usually only after a carefully constructed point.)
In the upper sequences he hits his "typical" rally shot of a waist high ball, with his follow through well above the shoulder.
And in the lower sequence he hits a low ball, again with the pronounced "low to high" swing bringing the racquet well above the shoulder.
But even though we are missing the side views to show it, I can assure you he has that long "through component" demonstated by Pat Dougherty in his video.
As for the serve, many hit their second serves without pronating.
You need to pronate on the second serve to have that "pop" as well as well as the spin.
And here is the key: you've got to get the racquet well to the right side of the body on the second serve.
Too many have the racquet drop in the middle of their back so as they bring the racquet up they just brush up on the ball.
They can't pronate because it just is not possible to pronate right to left if you start in the middle of your back, rather than well to the right side of your body.
In the above great stop action kick serve sequence Toly has posted here before, you can see how far to the right Sam Stosur has her racquet in pic1 - and how she maintains the racquet well to the right side through pic 7 as she aims the butt of the racquet at the ball. (She is bringing the butt of the racquet up at the ball almost as if she is going to spear it!)
Once the arm is fully extended at the elbow (pic 9),
the next major motion is "pronation" as she moves the racquet head from right to left in pics 10-16.
That right to left movement (pronation) is the "slap" which really gives the "pop" on the ball.
Notice that during the same pics of 9-16 that the racquet head is also rising, and it is this "low to high" motion that will produce the spin on the ball.
Also notice that for any spin or kick serve the point of ball contact is somewhat lower than on a first serve - it has to be to get that low to high motion.
Do all the above -that's how you get "pop" and "spin" on a second serve.