Once they take off, they grow fast. I didn't have to mist mine, but they were in the fish room, which was plenty humid, so that might've helped.
At the advice of the grower, I used styrofoam to suspend them in the water and stabilize them, and their roots grew downward and took hold in the sand bed. At that point, I could remove the styrofoam. I loved how they looked with the roots growing down into the sand, and fish/crabs moving around them. They don't do well if they're getting buffeted about a lot by the current. They very much prefer to be stable.