Basically spritz them with water rather than water them. They don’t mind being not watered, but if they’re too damp, the roots go mouldy and they die.
If you think yours are overwatered, and they’re still in a plastic pot inside the container, put the plastic pot on a wad of kitchen paper overnight, and it will help soak it up.
That diagram’s for a thing I was writing about repotting succulents in closed pots. Basically you put a layer of pebbles in the bottom for drainage, then a layer of activated charcoal to stop fungus and mould growing on the roots, then special cactus soil which is loose and mixed with sand, and then another layer of pebbles on top. That makes sure there are no damp bits lurking inside.