misting and humidifiers solve two different proplems.
misting is for chameleons to drink off the leafs of plants.
2 to 4 times per day is normal.
most chams like a dripper too, so you can cut down on the misting sometimes if you also drip.
with a hand mister, pull the trigger slowly to create small flying drops in the air that will land on the leaves. DON'T pull the trigger fast regardless that it will create a "mist" in the air...I find that this mist scares the crap out of our chams, and while I'm new, I've now tested this out on 3 chams and they all hate it. so pull slowly so it will be like tiny rain drops.
try to mist above the cham or away from them. not directly on them, especialy if they are small/young.
you should mist, off and on, for a total of 3 to 5 mins.
your humidity should go way up after a misting. say from 50% to 90% after you are done. analog hydometers take a long time to go up, so it might only read 70% when you are done, but might still go up a few moments later.
adding more plants will help with humidity when the cage is dry (between mistings).
but like me, there is only so much plants can do when the air is bone dry in the room...I'll bet that right now your air is getting real dry like mine is.
a cool mist humidifier will not help with drinking regardless that chams do get moisture from the air.
what it will do is add humidity to your room air and thus your cham's cage.
while I am not directly pumping the fog from a humidifier into any cage itself, once I get some quads, I'll be pumping the fog directly into the top of the cage with pool hose and PVC pipe.
some good examples of direct cage humidifying can be found here...
http://www.chameleonnews.com/?page=article&id=72
(one day a quad will come home to me, one day

)
Harry