If I can, I try to use a pump with a car-filling nozzle as opposed to a truck-filling nozzle. Usually, a car-filling nozzle will stay on with it set on its lowest filling setting.
When using a truck-filling nozzle, as pointed out in earlier replies, it helps to point the nozzle towards the rear of the coach and not insert the nozzle far into the fill hole. I use a long standard screwdriver to hold the fill nozzle at a setting that stays on. Be careful though, with the nozzle being held open with a screwdriver, piece of wood, etc., you run the risk of the nozzle not turning off when it senses the tank is full. ONE TIME I was not close by when the tank overfilled because the nozzle did not automatically shut off. I estimated a quart or two of diesel spilled down the side of the coach and over the island making a mess.
Stay close to the nozzle and you can hear the sound change when the fuel starts backing up into the hose between the fuel tank and the fill hole.