That was far too much water to add to the substrate. If you can, leave that tub pulled open a few inches until the water gets a chance to evaporate some (that is, if you have an empty tub to put that snake into).
I would also drill or solder more holes into the tubs. It is a lot easier to add humidity if the tubs are too dry than it is to dry them out if you get them too wet.
Generally, you shouldn't have to add water to the substrate. If shedding is an issue then either provide a humid hide for shedding purposes or add a small amount of water at a time to the tub. I generally add water to the warm side of the tubs and underneath the hide - the warmth helps the water evaporate which is better because you are looking to increase the humidity in the air, which means you don't necessarily need damp substrate. Plus having it under their hide allows for the humidity to be trapped in the tub for a little bit longer.
One other thing you could do is start a regular regimen of daily mistings. This is probably the easiest thing to do and allows you to have much more control over how wet everything gets.
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Stay United!

I'm still not sure if it's weird that my best friend is a two year old boa named Ronin. He's quiet, non-judgemental and listens... what more could you want?