I have a badly alligatored plaster ceiling that needs refinishing. I remember hearing about self leveling battens to take out any surface unevenness when I affix new sheet-rock over the old plaster. It is not possible to re-skim as the plaster has lost contact with the lath underneath. Any suggestions?
I have never heard of "self-leveling battens" but I am familiar with the job of repairing damaged plaster ceilings.
In my own home, I had to repair a 2 inch sag in the middle of the living room ceiling before covering the whole thing with drywall. To repair the plaster ceiling, I installed 1 x 3 furring strips on 24 inch centers across the entire ceiling. Then, using cedar under course shingles, I shimmed between the furring strip and the old plaster to get the entire surface as level as possible.
The end result was a smooth surface upon which I was able to attach drywall, then spackle and paint. Since drywall isn't very flexible, it was necessary to do all this to get the surface flat enough.
In your case, you might not have to use furring strips when repairing the plaster ceiling. If the old plaster is simply cracked and the frame of the ceiling isn't significantly sagged, then you can simply go over the old plaster without installing furring strips.