Not sure about the above (vid) technique although I am sure it would work for some. As for going faster downhill on the road/cornering on the road, personally I stick to the traditional method (off road, is different), but definitely try and learn/adopt the Cancellara dip you will see in the above video; it’s excellent for those times when you just need to tighten up a little toward the end of a bend.
Also not the most exciting or insightful piece advice ever but, practice is the thing that will make the most difference. I used to be super confident downhill on the road, happily sailed past cars at 45-50mph but then didn’t have a road bike for quite a while, for a few months after getting a new one I was rubbish, no confidence at all, I almost gave up on the road bike, but now back to feeling pretty confident…although not quite the luxury of the quiet roads I used to ride on, sigh.