It is the one thing that bugs me about those A's, putting gas in them with any can, hose or spout, it a battle not to spill gas on them. i carry a small 4" funnel in a zip lock bag to make it a little easier.
I live in Massachusetts and every Mobil station I have ever stopped at has a modern vapor recovery nozzle which allows easy Model A fill ups. With other brands of gas yes the stations often have older type nozzles that are a real problem for a Model A fillup, so it then becomes a matter of chance on filling up a Model A.
Go to a Harley store and pick up their vapor recovery hog lock thingy (I don't what to call it). It looks like a hog and when you pull the recovery hose back there is a ferrell there that you slip this pig over and it keeps the hose back, you can then fill up w/o holding the rubber part.