Hello Blanco1,
are you going to have to replace the ceiling or just the plaster finish? I had a similar problem except i had to replace the sheetrock ceiling and then replaster the ceiling. To get those swirl mark's you can use any tool that makes the desired swirls you like, and how "rough" or "smooth" of an apperance you are after. sponge's, paint roller's , finishing trowels all can give you a swirl effect. What we did was take a piece of sheet rock that was left after fixing the ceiling, and we expieremented on it using plaster and every tool we could get our hands on to make it look like we desired. we ended up sticking with a regular sponge and then to smooth it out we let it dry and ran over it with a trowel knocking some of the texture down. Good luck with your project and dont forget to look online for some tip's and pictures if you get in a bind.
Chris