Wow, great guide ... I just skimmed it. Izotope RX,which is mentioned, in the appendix, is amazing and I use it to separate noise from vocals for my podcast.
One of the authors here (justin), thanks for the feedback!
The goal of this tutorial is to show how you can use open-source tools to create your own RX :) For example, you can train it to remix/separate a specific set of instruments you care about. Cheers!
The dereverb that it can do is pretty amazing.