What species?
What size tortoise?
What size enclosure?
What substrate?
Open or closed top?
Generally speaking spraying the enclosure is ineffective. You'll need to dump water into the substrate to keep it damp. How much water and how often depends on many variables, and is different for everyone.
I'd make it with a closed top. You need to be able to control the heat and humidity, in an open top it's impossible unless you are lucky enough to live in a tropical climate.It is for a 2yr old redfoot, approx 5 inches. I am using orchid bark for the substrate. It is going to first be in a temporary enclosure of a 20gal Long tank with a screen lid because the turtle box is not yet ready. That is going to be about 5ft by 3 ft, I think, open top. I've been looking at designs and am building a custom box enclosure.