Jclaireborne, I don't think 6 inches of substrate is "wrong". I don't think I said so in my post?
I agree with this:
Some people keep deeper substrate and others use less. Personal preference really and there are advantages and disadvantages to both.
I am getting the feeling that you think I am responding negatively to your post, but that was not my intention. I was just trying to answer the OP's question and we do things differently, that's all. I'm sure your skinks are every bit as happy and healthy as mine.
As for soil, when I tried it, the lizard made an absolute mess every day, smearing it on the glass doors, throwing it in water bowl and such. Also I found it got all over the floor, and was very heavy to bring home. Perhaps I didn't do it "properly" as you say, but my current substrate seems to be working fine so I just never tried soil again.
How do you use soil properly? Is it a matter of packing it down firm?