Nice machine in the video!
When I read 'foam etching' in the title, I thought it is about the 'dish sponge + FeCl3 + PCB inside a zip-lock bag' method.
The sponge etching is very clean, simple, fast and economic. Just squeeze the sponge bag for a while, and that's it. It's a very clean method (simply dispose the whole zip-bag after etching), much faster then bubble etching or hot&agitated bath, and you don't need so much FeCl3 as in a bath etching.