"All You Need Is Ears" George Martin
dwardzala
I didn't watch the video, but placing an EQ before and after a compressor allows you to reduce unwanted frequencies (perhaps low freq build up) before the signal hits the compressor and then to sculpt the sound after the compressor. You can do it all before the compressor, but it allows a bit more control if you use two. I don't use this technique much because I really like the PC EQ and there can be only one in the chain.
This is a technique I use when i feel it's needed, using an Aux track for the second PC EQ works well for me.