They reworked the powered equipment training process a couple years ago, so I assume all DCs use a similar program now. I'm a trainer in warehousing so I have trained lots of newbies on the order picker.
The general training program starts with a small classroom part which is just some of the basic safety rules for driving around the building. Next you do a building walk where you watch others operating PIT and watch for safe or unsafe behaviors that you talked about during the classroom portion. It goes fairly quick so this will maybe take 1-2 hours.
After that the trainer should go over the controls and points of interest on the machine while referencing the operators manual for the PIT you are learning. Then you learn how to fill out a pre-use checklist for the machine.
After that its just learning basics and obstacle course stuff for a while, mostly driving around cones, pallets, or cagecarts, depending on what is available. Once you are comfortable with the controls of the machine you move on the driving in the racking aisles and driving around the building. Once you hit about 10 hours of training you take a test which involves a few questions and then a driving section, both parts are completed with your trainer and OM watching.
Passing the test means you are certified on the machine and start to learn the actual job function. If you don't pass you practice the parts that you missed, and try again the next day. You get 3 attempts and only retake the portions of the test you missed.
In warehousing everything we do involves PIT so we start training our new TMs on day 1. My building also has new employees work half shifts for the first week, so we usually do the first exam on the 3rd day. If you have ever driven PIT before like a forklift it goes a bit faster and you may take the test well before the 10 hour mark.