Deflators are a fantastic item. I have these:
http://www.stauntyredeflators.com.au/I don't know anything about the Smittybilt ones, but they look basically the same.
One thing I suggest that you do, once you get them set to the pressure that you want. Put loctite on them, or run a bead of caulk around the threads, or do some such thing, to keep the locking ring from loosening up and letting the set point change.
I didn't notice that one of mine had loosened up, until I aired down at the start of a trip, walked away and chatted with others while the airdowns were doing their thing, then walked back to m jeep - only to discover that one of my tires had been aired down to.... oh.... zero pounds.
It's rather embarrassing to air up at the START of a trip.... especially when you're the trip leader.