Here's one the article links. They interviewed Kevin and he talked a bit about Mewes' relapse and how their podcast came about from that.
http://www.examiner.com/article/filmmaker-kevin-smith-dishes-about-act or-friend-jason-mewes
Another article link of interview with Mewes,
http://www.thevine.com.au/entertainment/movies/jason-mewes-of-jaysil ent-bob-i-almost-set-myself-on-fire-i-almost-went-to-jail-20120305-244 286

Thanks, will give it a listen. I kind of wish Kev had written an essay about it like "Me and My Shadow" since he has such a way with turning a phrase, but I think he's abandoned blogging in favor of his podcasts exclusively now.

Sure! Yeah, the first couple episodes they leave us hanging but they finally talked about it between episodes 5 and 6. Episode 5 when they found out that Jason fell off the wagon and that he has been hiding his drug use for a year and been lying (i.e. he's broke, have nothing to do, no acting gig hence Kevin lending him a hand by hooking him up as stunt driver for Cop Out)- Kevin cut all ties with him.
Episode 6 talks about Mewes still messed up on drugs after he and Kevin are estranged till Mewes decided once and for all get his stuff together and checked himself into rehab.
Mewes is really lucky to have Kevin always being there for him- even starting a podcast to help keep him on the straight and narrow. It looks like it's helping since he's been sober for almost 4 years now.

Thanks, I remember listening to the first six or so of "J &SB Get Old" and they kept saying "we'll get to the story next time!" Is there a specific episode number where they more or less cover the whole thing?

I suggest you listen to the first 6-7 episodes of "Get Old" and you'll get info on Jason's 2009 relapse. I believe it's around the time when they were getting ready to shoot Cop Out till Jason's wife brought it to Kevin's attention that Jason fell off the wagon- hence Kevin fired him.