While giving them baths is not a bad idea, although I use other methods, leaving them in the same water for a couple of hours is a bad idea, for the water, although warm when administering them to it, quickly cools off to room temperature, which is downright cold for them...
When I get in a new tree monitor/s, I set them up individually, to make sure I can "monitor" their progress. I have just thought of a new idea for ICU/quarantine/hydration chamber, in which I am utilizing a 50ish gallon rubbermaid garbage can, with an acrylic cover to prevent escaping humidity. There is a dome lamp attached directly into the acrylic to provide ample heat for the monitor to achieve optimal basking temps. I currently have a tiny black tree monitor girl in there now, as she came in very dehydrated and thin(not much to do with lack of food, just water). I mist the enclosure several times a day, and keep note on whether or not she is drinking volountarily.
The first day I set her up in there, she began drinking immediately after spraying her(as if she hadn't drank in weeks), and, although I normally do not try offering food for at least a week or so, I felt that she might accept a chopped up hopper, and sure enough, it was gone within an hour of me putting it in there... So, in the quarantine "can" she stays, until I feel that she is healthy and hydrated enough to be set up in a more permanent enclosure.
I have also used equal volume(roughly the same volume) rubbermaid/sterlite containers in the same fashion, however, I prefer this new tactic, as for tree monitors, a garbage can has much more verticle space, which allows a better verticle temperature gradient, and oh yeah, of course, allows them to climb a bit more....
I hope this helps you out just a bit... But like I have recommended to other people, I would suggest separating the animals if you do have them together.. Worry about eachother's own health first, before worrying about them being together.... In my experience, this seems to be the best method as far as successfully acclimating tree monitors...
Take care,
treevaranus(odatriad)

The Odatriad