As for swabbing between shots with BH209. No you don't have to. But then again how long does it take to swab between shots? <1 min. with a spit patch and dry patch? And really, if you think of it - how many shots do you take at game while hunting? One, two at the most.
I will agree that BH209 is not hygroscopic. That is a definate plus when hunting in wet weather. (something I don't do anymore unless I am on a guided hunt) But I've left my Hawken flinter loaded an entire season many times with good old black powder in the damp wintery conditions of PA's January ML season. And it went off when I needed or wanted it to.