I'm not an expert; I only have one crestie but is it helpful to mist them. It's especially good if you have a planted tank like I do. The problem with the waterfall is that if it's a baby it might drown in it and otherwise if it poops in it, it fouls the water and you have to keep cleaning it out. I mist daily and have a ceramic bowl set into one of the back corners of the tank which increases the humidity and is a place to drink from.
Yeah you really should mist them, I do it 2 times a day you might be able to get away with doing it once. Usually if im going to be gone 2-3 days on a weekend or something i put in a little water dish to help keep humidity up.
I also mist mine at least once per day-usually at night
I really don't like reptile waterfalls and fountains-i think that they can harbor all kinds of nasty bacteria if not cleaned often both on the inside and outside
-but that is just my 2 cents