I use a mixture of ~50/50 perlite and "reptile moss" from the pet store for my snake eggs. I had hatched 4 clutches this way in the past and it seems to work. Perlite is fine just make sure when you open the bag for the first time that it doesnt have a chemical smell AT ALL. If it does, use different stuff. I fill small tupperware containers with the above mentioned combonation, soaked in RODI water oivernight, then squeezed out until no more water drips. I then set these tupperware in a shallow tub filled with water and a aquarium thermometer set at 80*(snake temp, chams are different).
IF condensation forms on the side of your container thats good, if ALOT forms and is actually making solid droplets on the top of the container its to wet. If to wet leave the lid open. If to dry put a soda pop cap filled with water in the container, dont put water directly on the eggs.
thats all for now....my snake is laying eggs RIGHT NOW and i need to go see if she is done so i can transfer her eggs into the above described incubation chamber.....yeehaw