Furloughing is just a way to keep your employees while not having to pay them. I would say that the only reason WDW kept their cast paid for the past month was because they weren't certain if this would blow over fairly soon. However, things have changed and this has gone on for about a month. I think there is a realization that this may continue for another month or two. In that effort, I think the furloughs are the first part of the plan to reduce as much cost as possible and then start to focus on how to operate with no profit flowing in.
As for reopening, it is pretty cloudy to truly determine what will happen, but there are things to consider as far as the setup goes. I would be confident that it may take one or two days at most to ready the parks as far as the standard cleaning goes. At this point, their food supply has been reduced to items that don't expire or have a very long shelf life, if everything isn't already gone. Restocking food will take some time. Shops may have packed up inventory, or secured the more valuable items. This may require a full and complete inventory of every item as well as resetting store displays. Another things to consider is the actual cleaning itself. Standard cleaning measure may not be so standard anymore. They may have to go through and sterilize entire shops, restaurants, bathrooms, etc.
As far as training is considered, there shouldn't be extensive training. The most in-depth training needed, would likely be on how they implement social physical distancing into the theme park/resort environment. As well as any significant changes to cleaning procedures. Depending on the location, the cleaning procedures shouldn't be difficult to train, but the physical distancing will vary and for some areas will require some reimagineering on how the task is performed. For example, security bag inspections. Some places use sticks, others just use hands. The problem is regardless of a stick or gloves, etc. germs will still easily be spread from bag to bag, and those measures only truly protect the actual employee not the guest. Parks may very well have to switch to x-ray screenings for bags. It is a system that doesn't involve touching unless a suspicious item is viewed on a screen. This would require extensive training and retrofitting into existing park design.
All I can say for sure, is that until there is some expectation/trust that a healthy environment can be ensured, things will not be pleasant. I can only believe that this pandemic will change our lives much like the 9/11 attacks. In response to such a crisis, new measures were implemented over night. It took awhile for those measures to be common-place in society such as tighter security inspections. I can only imagine the same for tighter health requirements.