That's an excellent question - I hope I can give you an answer that will do it justice.
After the plunger had been removed from the hot glass, the bowl would have been "snapped up" - i.e. picked up by its collar base using a tool called a "snaps" (similar to a punty). While hot (very hot) it would have been first shaped (if desired) and then iridised - with a possible visit to the glory hole between times.
Holding the hot bowl by the collar base, using the snaps, the handler would have lowered it onto a specially shaped apparatus that would crimp the edges.
I wrote an article on fine crimp edges (a very tightly ruffled edge) in 1999 that the late Frank Fenton kindly helped me with. He explained it like this (I'll quote him):
"the item is taken up in the snap to be removed from the mould - then, when still hot and malleable, it is pushed down onto the open bottom section of a shaped apparatus known as "the crimp". The top part of "the crimp" (which is hinged in two sections) then closes down onto the piece to form the Fine Crimp edge."
The crimp would have been operated by a foot pedal when Carnival was first made, though Frank told us that later on they "got smarter". A relative, Jim Fenton, developed a way of utilising pneumatic power to operate the apparatus.
You can see some fine crimp edges in this article - plus more on how that particular edge was made.http://www.carnivalglass.org/education/candy/index.asp
I think I'm right in saying that some shaping would also have been done by hand, and any tool marks could have been fire polished out by returning the item to the glory hole.