I use mist systems, but once a week or so, I put my chams in the shower for a prolonged rain. They do seem to like the mist or secondary splash of the water more than being in direct rainfall. I put sandblasted grapevines in the bottom of the tub, a screen over the drain in case they defecate, and keep the bathroom dark.
Be careful to not get it too hot and steamy in the room, as this actually dehydrates.
Regarding bathing: I have done this for several species, from brevs to melleri, but only as a medical therapy. A lukewarm soak can move the bowels or eggs. When used with a few drops of Nolvasan concentrate or antibacterial hand/dishwashing soap, it can be a helpful treatment of those horrendous foot wounds (ulcerative pododermatitis) found on WC chams.
I found a couple long, shallow, and narrow Tupperware containers and they are my "official" melleri soaking tubs. The water level is roughly 1-2" deep. I set the container in the bottom of my tub; if the cham should climb out, it can't get into trouble or contamniate its feet with a dirty surface. I also keep the room dark, and fix a firm headrest under the cham's chin to prevent it from submerging. I used to use empty TP rolls for this, but I switched to a solid resin chin rest that does not want to float.

Smaller species need a submerged towel to grip and your finger under their front feet or chin for safety. I soak once a day, sometimes twice, as long as the foot wound is open. If soaking a new or WC animal, I clean the entire tub and soak container thoroughly after each use.
Here is one WC melleri just put in to soak for a foot sole wound. She hates the camera.
Here she is, a couple sessions later, drying before I put ointment on the wound and returned her to her enclosure.
She healed beautifully and actually became a little more tolerant of me after she figured out the daily rhythm. She may have associated being handled with a pleasant sensation of the soaking? Now that she's out of therapy, she's gone back to hating me properly.
This kind of bathing therapy does not involve pouring water over the animal. I don't restrain the chams in any way. The warmth of the soak encourages the cham to settle in and nap, of its own volition.
If you are trying to hydrate and not heal a wound, go with the shower method.