I don't measure the humidity. I use the coarse grade of vermiculite and add enough water that when you take a handful of it you can only squeeze a drop or two of water out of it. I put two tiny holes in the lid of the shoebox sized container and lay the eggs in dents in the vermiculite and put the lid on.
Once its set up to incubate, the sides of the container and the lid will have beads of moisture on them. I incubate them at about 74F.