Sheesh, I guess you missed the gigantic picture I posted. The "Comment deleted" was a quote from you. What, exactly, is this "poke the can" you're talking about? And, I'm not sure, but I think the propellant is Co2, which obviously is what we breathe out.
Have you ever tried getting paint out of a can without a straw? I had a little metal cup. As soon as there was paint at the bottom, it was all shooting out. It was a failed attempt at getting paint out of the can WITHOUT a straw.