One thing that I find interesting though is that about 30 OFBiz based ecommerce sites went live (that we are aware of) without any interaction from Andy or me, and without the conveniences that are now available such as the Basic Production Setup document, the training videos, the Undersun online documentation, etc.
I imagine that some of the people working on these learned things from the mailing lists, but my guess is they took the approach of considering the code base to be a rich resource of examples, and used those examples to figure out how to do things... That is mostly a guess though...
In fact, my opinion on this topic is that there is a LOT of functionality in OFBiz, and while you can learn the basics of the framework and tools and a week (not easy, but possible; and only a general understanding for sure, not all details available), it can take many months to learn about all of the data model and the logic and the user interfaces, basically all of the business level stuff. So, no matter what materials exist it will take time for your brain to soak everything up, and the examples are by far the richest and most dense resource for doing so.
All of the other documentation and videos and such are really only meant to make it easier for you to get started. They won't finish the process, and no materials ever will, because your needs may be pretty unique and it is impossible to predict what they will be and write a document that gives step by step instructions on how to do everything that anyone might want to do. At some point, some live human effort is necessary.
So, the documentation offerings from Undersun are NOT necessary to get going with OFBiz. Dozens of people are doing great things without ever looking at those. However, they can help you to get started and that is their intent.