This is what I use , I put soil in the bottom ( helps stability and gives moisture which in turn helps with humidity) I then put shavings on top, I have very good hatch rates using this method, one thing... two days before the eggs are going to hatch throw the Broody off the have a crap, when she goes back on turn the drum around to face a wall that way she won’t try and take any early chicks to feed leaving the others that are due to hatch.