Working on this most recent Izannah doll, I used the regular Krylon matte varnish, as I have for ages.
But I'm not sure what happened! No unusual material/paint/coating under the varnish, so maybe it was a factor of temperature or humidity? At any rate, there is a very slight crackle effect on the lower part of this doll's face. As it seems not to affect the adhesion of the paint or varnish, and it is subtle enough to actually enhance the doll, I left it as it was. (Also, I didn't want to totally repaint, since I was happy with her at that point!)
Maybe I'll figure it out, but I doubt it.
Guess we'll see--I've got a set of boy & girl twins to make now!