I've never heard of this method. Do you have any "before" or "after" examples, or may just an "after?'"
ghopper, were you asking me that question?
If so, I don't have any examples of that method, I am a "designer", I just
thunked 
it up just before I typed it out.
I've used Plaster of Paris for lots of "fixing" jobs.
It works great for restoring old picture frames (
see below) that large pieces of the plaster "design" has broken loose and been lost.
Just select a portion on the frame that "matches" the missing portion, .... place Cliing Wrap on it, (
or you might even use Vaseline) press it down snug, .... the put 1/2 inch of Plaster of Paris on top of it.
When the Plaster hardens ...... you got yourself
an "impression" mold.
Then you fill the broken section with wet plaster and then "press" your mold into it and lift it back away and "Za Zing", you got a repaired frame. And a twice-over with a spray-can of "gold" paint and it is ready to hang on the wall.
If small pieces, 1" to 2", are "missing", just put a "glob" of plaster on it and "form it" with your finger, a small artist paint brush or whatever. And it doesn't have to be perfect because after you paint it, you will never see it ..... unless you are looking for it.
I use to buy those cruddy ole frames for $1 to $3 each, recondition them, and then sell them from $35 to $75 each.
I still have 2 of said frames, hanging on the wall with pictures (pastels I think) in them which I need to post to get your all's opinion on.
