Never had any success with eggs incubated in dirt/soil. I've used coarse grained vermiculite for years. I don't know what you mean about foil either.
This is what I do...I use a shoebox sized tupperware type container with a lid. I punch two tiny tiny tiny holes in the lid. I moisten the vermiculite so that when I squeeze a handful of it no more than a drop or two of water comes out. I fill the container half full of the moist vermiculite and make slight depressions in rows in it with my thumb to put the eggs in. The space is to allow air circulation and room for the babies when they hatch until they can be taken out of the container. Once the eggs are in the container I put the lid on and put the container where it can be kept at about 74F. IMHO 85F is too warm. Beads of moisture will form on the inside of the lid and walls of the container.