Revealing mistake: As Ironbar shoots into the conduit where the kids are, the spots where the spark charges to simulate the bullets hitting are visible.
Revealing mistake: When Savanna first finds Max in the desert studio lighting is seen behind her - this is too low and bright to be light from the moon and can't be light from anything else as they are in the desert miles from anywhere.
Revealing mistake: At the start when Max is knocked of his truck, the plane circles and the shot switches to in front of the camels. If you look at the ground you can see the tyre tracks from previous takes.
Chosen answer: Actually grooming would be somewhat important, if only for general comfort. Unruly facial hair can be quite uncomfortable and gets dirty easily. It is entirely plausible that men would regularly shave if they had a means to even in a post-apocalyptic wasteland.
BaconIsMyBFF