Vader had a lot of time to contemplate his mortality. His motivation to overcome death could have lead him to the same techniques that Qui-Gon discovered, and we all know Anakin was strong with the Force. Not like he had a social life - it wouldn't surprise me if he could have discovered it on his own. Confirmation of that would be nice though.
***MINOR SPOILERS FOR BoBF FINALE***
-- I thought it was alright, but I wasn't expecting much more than what we got. The writing on this show has been fairly simple as crime dramas go.
-- There's way too much time spent with the good guys shooting at the battledroids for no reason. It's clear shooting has no effect, so it's pointless and there's no drama to it other than to give them something to do.
-- Fennec has a nice "Leon: the Professional" sequence.
-- Interesting variation on the theme song at the end. Not sure if I like it or if it's just goofy...