You're right - its really hard to find reliable first hand info on breeding fire skinks. I have a breeding pair and have my first eggs in the incubator at the moment. They should hatch around the beginning of March.
It seems that the biggest problem with these guys is getting the eggs out. I have two ice cream tubs full of damp soil, with small holes cut in the lids. The skinks love to hide in these. The rest of the viv has an inch of bark chips. I found the eggs in one of the tubs. I set their viv up like this so as to facilitate finding eggs and I guess it worked. If you have deep substrate throughout the viv you will never find them!
My problem is that the skinks will continue to use the tub whether or not eggs are present, and so they might get damaged. Its not that easy to check these tubs, and you have to remove the skinks to do so.
It ought to be possible to have a deep naturalistic substrate and incubate in situ, but I haven't tried this.
Anyway, of the three eggs laid, two were damaged, and one was ok. This has been in an incubator (fairly moist vermiculite, 84 degrees F) for about a month and is looking good. I expect it to hatch (if it hatches) around early March.
I would recommend paying attention to calcium supplmentation and Vitamin D3. I use caclium carbonate ad libidum, with a Reptisun 5.0 and Nutrobal once every week or two (contains D3 and other vits).
I'm realy hoping for further bigger clutches...
Hope this helps,
Mark.