Adrian
I use witnesses and the witness forms. I understand those tech savvy people are writing mileage on receipts and photographing it next to the Odo, for start and finish (usually the intermediate ones as well). this goes on the other forms. I have also been led to believe that you can mix the forms. Starting with a witness and finishing with a photo, or vice versa. All seems to be getting a bit complicated. However it can be really useful when you get to the auto fuel station with no attendant or other witnesses. Just have to make sure the camera and phone are charged.
Have a good ride.