So it appears that an someone has a neat PR campaign going on that involves blood. I will tell you at the end what it actually is all about, but I found playing along a fun project. Over the summer Vice and other sites noted an ad for a Halloween rave party in Amsterdam where the organizers will spray people with real blood. But how do you spray people with blood? Which blood? And how much is a ticket? What is this all about? Read on for the answers.