We've been writing a weekly set of articles about the Frenzel at
freedivingfinland.net. The idea is that we go through a part of the technique each week and introduce a set of excercises that the reader should master during the week, before moving on to the next.
For someone who read, understood and succesfully applied efattah's document, there isn't anything new. But for someone struggling with it we breaked it into small parts that should be easy to digest and also tried to compile some alternative excercises that have popped up for example in these forums.
It's currently running at week 3 and around week 6 or 7 we arrive at the whole Frenzel. Go and have a look!