Few questions about substrateless incubating.

[GPreptiles]

So my female is in pre-lay shed right now, and I figured I will ask a few questions about substrateless incubating method . Here it goes:
1. Is it ok, to use vermiculite or it's bette to use perlite?
2. Why do you cover the top with foil, before putting the cover on the box?
3. How do you prevent the condensation from dropping on the eggs (since it's pretty high humidity inside the box)?

I think that's all for now - thanks in advance .