For a russian tortoise? I would say non- hatchlings you don't need to worry about humidity too much. Just make sure it's not to humid, and too cool at the same time. You could make a seperate humid hide if you still want to offer a humid environment.
If your russians are hatchlings I would be more concerned than if they are adults. If they are older keep your substrate deep enough that they can burrow into it, then once a week pour abour a cup of water in one area. This will keep the lower level of substrate more moist. That way they can choose when they want more humidity. If you get a hygrometer then fine. All my adults are outside so I dont have one either. You want about 50% humidity for them. I go higher for hatchlings.