Give up trying to get it straight with moisture. I don't use wood glue like titebond because it contains water and water and balsa don't mix. I always get warps if I use wood glue, it's why I still put up with CA. Just today I was making a long hatch out of 1/4 inch balsa. It needs to be plained and sanded to shape so I had to use wood glue. It warped!
When it's time to cover you use the covering to remove warps out of wings and surfaces. When you get there several of us will help you out. It's just twisting the surface and shrinking the covering on the opposite side of the covering to remove the warp. Using water usually just makes things worse. The balsa will also warp toward the side of the wood you have wet. If you have a wing warp going toward the top of the wing you moisten the bottom of the wing. It's just easier to do with the covering.