There are 2 parts to the Backlot tour - the Special Effects Water Tank, and the tour trams. I was an attractions coordinator at Backlot about 5-6 years ago, my information may be a bit outdated.
The water tank has 6 basic positions - Greeter (welcomes the guests into the attraction, parks strollers, etc); Photocell (gives a brief welcome spiel and loads the show with the correct number of people); Dresser 1/Dresser 2 (find audience volunteers to be in the show, and gets them dressed in the rainsuites); Assistant Director (instructs the volunteers on what they are going to be doing, and makes sure they are in the correct place on the stage); and Director (the person who is giving the show). On busier days, another greeter or a stroller person might be added to the rotation. You would rotate among all the positions, likely ending up at each one a few times a day.
For the tour trams ("Shuttles"), when I was there, there were 3 basic positions - spiel, drive, and dock. Back when I was there, the "Spiel" position actually narrated the whole tour. Nowadays, it's an automated spiel, so the only lines the spiel position has are to tell people to watch their head/step as they board, and give an all clear to the driver when everyone is seated. The driver drives the shuttle through the tour route. And the "Dock" positions are unload (helps the guests exit the attraction); load (assigns guests to specific rows based on their party size); dispatch (assists with the loading, queue management, and making sure the shuttles leave the dock on time); and wheelchair assist (assists guests travelling in a wheelchair, straps down wheelchairs on the vehicles, and moves
ECVs/Wheelchairs from the load to the unload dock).
When I worked there, you were assigned to 1 particular rotation, and you'd be with the same people all day, rotating between spiel/drive/dock (and breaks), and you'd have the same dock position all day. Nowadays, I believe that has changed, and the computerized Cast Deployment System will assign positions based on schedules/who's due for a break next/etc, so you'll have more variety throughout the day, but at the expense of not knowing where you're going next.
It was a fun attraction to work at. Obviously, times and people change, but when I was there, it was a pretty relaxed group of people, who worked well together, and had fun doing it. We often joked that we were the "most ignored attraction in the park"
