If you still are having humidity issues with the tub, you can mist it, but you're using newspaper so I wouldnt do too much. Does your snake have a hide in his tub? If he does what I do is either use wet moss, or alternatively use cotton wool and tissue paper, wet them, put them in a teabag or those sock like water filters you put at the end of taps, or any thin cloth stuff, and shove it into their hide or by the entrance of it. Basically making it a humid hide. I guess you could do it on a larger scale, like use an actual sock, if you want the entire tub's humidity up for now.