Here is one thing that might varied from one person to another.
I actually do mist 5 minutes/ session.
and yes the water comes from the top to simulate rain.
I do not use dripper at all.
And, since i only use 1 misting nozzle for my herpmist, there is a spot where my chameleons can get away from misting if they choose to do so.
Majority of the time, they actually stay and drink the droplets falling on their mouth creases. When they had enough, they just run away from it.
I know several people actually mist 30 minutes. Their chameleons are healthy.
Do note the fact that I allow complete drying time in between sessions.
Any way that can deliver enough water intake without compromising the health of your chameleon is good.
Some choose dripper, some choose mister, and some combine the two.
Whatever necessary to do the job.