Actually with propping the side of the bator you can still put water in the rings, just not so much. What I do is I fill the rings to the top while it is propped. Sometimes I over do it but it will drain out. YOu'll just have to have a sponge ready to sop it up.
As far as what to use to prop it up. I use the sponges I had for my old bator. I just couldn't get the humidity up and used alot of sponges. So how I have them not being used so I use 3 stacked. They are the thinner ones about an inch thick. So I put them under long side in and only aobut an inch or two sticks out from under the bator. I just gently raise that side to remove them and then move them to another side by gently raising the bator.
What I use to add just a little water is I insert a straw in one of the holes and use one of those big syringes that you shoot basting stuff into meat with. I use the syringe to put water in the straw and I can direct the straw where I want it.. Works for me.
I'm really trying not to open the bator any more than I just have to.