If you watch The Walking Dead then you most certainly have questions (aside from wondering if they really tried to fool viewers about Glenn's "death"). Your number one question was asked and answered on Talking Dead last night by The Walking Dead's comic creator Robert Kirkman.
In the midseason finale, Rick Grimes (Andrew Lincoln) decided it was time to break out the old zombie disguise trick. He and Michonne (Danai Gurira) cut open two walkers and covered bed sheets with their warm (are they warm if the are the undead?) guts in order to create zombie ponchos. This way they'd be able to walk through the hordes of zombies unnoticed, the smell of the undead covering the smell of the living. It's worked for Rick and Glenn (Steven Yeun) before. So if this is such a smart play, then why don't they cover themselves in guts when they're out on runs? Or when they were living in the woods before Alexandria? Why not just disguise themselves as zombies all the time? Well, because.