I would have to say the only "How to" spank videos I've ever liked came from Nu-West. I haven't been able to find them, over the years I've lost my originals. But I remember one with Kiri Kelly and Peaches and it was a really good one.
Anyway, all other since then are pretty much laughable to me when it comes to them showing how to spank. The swats are silly both the impact and the way the Spankee swats.
In addition many of them make mistakes in their videos that, for me really stand out. So now you should be able to see the big mistake both for the Spanker and the spankee.