I can give you my experience if you like. Last winter all of my tubers which survived were kept bare root. A. paeonifolius was stored in my bedroom in an open cardboard box with a label. When the weather began to become a bit less inclement I potted it up and put it in my greenhouse. I commenced regular warering and checked it regularly for growth or signs of rot. As it happens I lucked out and from now on will not pot anothing which does not have a noticeable shoot coming out of it.

I moved all of my house plants into either the house or the greenhouse about a month ago and all of my amorphs still show no sign of stoping. Those which went dormant before this process have been cleaned and are being stored dry like last year.

If your plants are still growing I'd water them. If they are stable I think you could safely stop watering them and see if this directs them into dormancy.
Do not cut off your stems. The tuber which is probably already forming in your pot needs all the food it can get and one way it does this is to cannibalize the old petiole and leaf. Once these dry out, or if they slough off in a pool of goo you can remove them.

"Once I remove the tuber from the pot, should I use sulfer powder on it?" If it makes you more comfortable sure. Remember that unless you really cut up your bulb or damage it then the outer skin of it should be protection enough. There is no sulfur powder in nature. I do not have experience with species from the more tropical growing regions, but the more temperate ones do not seem to need it.

I would agree wholeheartedly with everything said so far.

There is only one tip I would add.

If you feel more comfortable powder your tuber/s with cinnamon. This is a natural fungicide that will help ward off potential rot.

Think of the tuber as a potato tuber.
Store in cool, dry, low humidity, and no light conditions.

Check ebout every 2 weeks for rot or resumption of growth and only plant when it has truely begun new growth.

I have a few tubers that literally took 2 or more months to really begin to grow again after the first signs of continued growth.

Hope this helps.