I am not sure of the exact ratio, but I usually just mix enough water in to thoroughly saturate the substrate, and then squeeze all of the water that I can out of it. This has worked well for me for years. If I see an excess of condensation on the sides of the container at any point, I leave it open for a few hours to let it dry out out a bit. I have used various substrates over the years and found them all to be effective. This year I used vermiculite as the base substrate. I nestled the eggs into the vermiculite and then laid a layer of sphagnum moss over the top.
-----
www.sunshineserpents.com