I have several videos on the narrow gauge when D&RGW was running. I put a lot of effort into finding the Farmington Branch on film. In my opinion, the best one for the Farmington Branch is “Denver & Rio Grande Western and the Bumbleebee - No. 268”. It has some good Farmington and Aztec shots, plus shots along the way. If I recall correctly it also has Black Canyon. Green Frog produces this one and I got it around 1997.
I also have “Twilight on the Rio Grande” from Green Frog it has some nice shots of the mainline to Durango and little bit about Farmington. It is nowhere near as nice if you are looking for Farmington Branch information.
Once again, it is only my opinion. These two helped my find what I was looking for.