I wish I could help you but maybe a good greenhouse person or maybe the local garden society could direct you.
Thanks
bls

Your plan sounds spot on. I have some tubers just inherited from my Mom who recently passed on, and over the past 6 years or so I've fostered them for her in an attached garage whose temp goes perhaps as low as 55F. I'm not sure what one would do to force them. Have always kept them in their pots (I just barely cover the tubers) til I begin to see sprouts. Then I repot them in fresh soil for the coming season and introduce them to the outdoors as weather permits. Once in a while during the winter (less than once a month) I notice them and water the pots to keep the tubers from shriveling completely.
Recently I've begun to wonder if I'm planting them deeply enough, though. Perhaps the stems would be stronger if they were deeper in their pots.
I am a relative newbie with Begonias, and kind of gleaned this process from experience. Perhaps someone with more knowledge will pop in here.....
-perL