This seems to be showing a guy aiming a cellulose insulation blower at an open wall, and somehow the insulation is sticking to the wall in perfect strips. What is really happening? This is from the Home Depot web site.
Google 'wet spray cellulose insulation'. You'll see videos etc where they spray messy then scrape flat. The kind folks at HD obviously had helpers scraping (and cleaning up the guy doing the application...)