I guess I'll add my opinion too.
Filter/ mouthpiece: Small rolled posterboard/cardboardish cylinder in end of joint. I find that it helps me roll by giving me somethin solid to shape the rest of it around. Also you can smoke all your weed. Also if done properly it won't collapse or shut itself from saliva, it's a lot more like smoking a cigarette. You can actually pressure your lips around it to draw in smoke, with just papes it seems like you pinch it shut when you try to do this. I prefer this method, but will smoke any kind.
Roach: Leftover resin soaked paper + tiny bit of weed. You can save these and throw em in a bowl. I also find that putting it in the end of a one hitter (batty) usually lets you smoke it all. As far as rollin it into another joint (or that crazy 8th gen deal), I can't help but imagine that gets pretty gross pretty quick while not adding a lot to the experience.
But seriously, could they not have just rolled a real 3rd or 4th gen joint? That would actually be neat to see, but why do they think 8 gens is impressive when it is pretty impossible? Sorry to get hung up here, but was there a point in doing the math past what's feasible and then making that the benchmark? Ever had a 8th gen joint? If only a few people have ever done a 2nd gen, why speculate. I dunno...
So yeah I do a mouthpiece/filter in my joints (few and far b/w) but have no problem with any kind of doobie.
Smoke it