MrsA that is a very interesting question.
She implements some kind of CM-voodoo.
When DD started off with the CM at 6 months, I sent a dummy and her comforter with her since there would be no boob. I was really worried about it actually! So for the first month or so she gave her the dummy at naptime and I'm not sure exactly if she rocked her a bit or just put her down and let her get on with it.
Then we figured out here that DD doesn't need the dummy for naps - DH was able to put her down for her weekend morning naps with just a minute or two of rocking so we ditched the dummy. It has since come back at night, but we don't use it at all during the day now. So it doesn't go to the CM.
So! I believe that the CM puts DD down for her nap, gives her her comforter, and leaves the room. Apparently she complains for a few minutes - sometimes - and then goes to sleep. According to the CM, DD2 has been the quickest baby to settle for her so far.
Honestly, these babies would make fools of you - DD2 has NOT been an easy baby but I think having DD1 there plus a fairly structured day to begin with (thanks to DD1) has just helped ease her in. Also babies will do all kinds of things for childcare workers that they simply won't do for parents. I can't just put DD2 down in her cot and walk away at naptime - believe me I've tried! However she will go down easily for her morning weekend naps without boob, always under 3 minutes of rocking. I think babies tend to be so exhausted for that first nap that they go down for it more easily than others.
Sorry, that was a bit of an essay!