Keep soaking him and give him a waterbowl. Even if he doesn't drink, it will at least benefit his skin, so I feel. True, they usually drink in a more natural setting. I wonder what keepers of captive bred russians would say? Anywho, I've noticed they also defecate when soaked, and I believe this relieves constipation before it becomes a problem (very commmon problem in torts, the first thing to check for in a noneating animal). Also, check the eyes. If over a period of time you notice the eyes becoming drier and more sunken in appearance, it probably means you need to keep the animal in a bath for longer. Keep in mind that they do come from a very harsh environment and are accustomed to living without water for some time. This doesn't mean that they can go without it, but it does mean that they have a wide range of tollerance, unlike leopards or redfoots, for instance.
T.G.