I have a 2520, and I use a Type II safety can. The built-in nozzle is good for getting the diesel in the hole. The metal cans are a bit heavier to lift up over the hood, but I don't like poly fuel containers. But it's still real easy to over fill it because you can't see into the top of the tank as you pour. I tend to not fill it up completely, and just call it good enough.
That's what I do. I use a 6 gallon yellow plastic Rubbermaid container and normally I only have about 4 gallons of fuel in it. With only 4 gallons in the container it's lighter and it does not start coming out the instant you are trying to get the spout in the filler neck on the tractor. I also rest the container on the steering wheel while filling the tractor, have to caution you here as it is best not to have the tractor running as the steering wheel will easily move all over the place because of the power steering and you will have fuel all over the place also (just guessing hereOne trick to keep from overfilling: when I fill my 2320, I leave the key in the first position, so I can watch the fuel gauge as it gets to full. On mine, it's full when the needle's just past the top of the gauge.
I agree the safety valve keeps fuel from getting everywhere, but 5 gallons of diesel gets pretty heavy after a while!