I'm with you,
@Njordr. I'm anticipating a warehouse chain (BJs) will give me $.50 discount up to 40 gals when my register tape hits $150--which I can do, easy. So I'll drive up empty with 4 5-gal cans. A few thoughts:
1) Before the transaction, I have all my cans out, caps off, so I don't accidently shut off the pump and lose my 2nd 20 gallons. This also signals people behind that I might be a little while.
2) Don't ever use any kind of "safety flow" "handy trigger" "No-Spill" or anything like that. I end up spilling a lot. This type of spout is the worst of all:

You want smooth, gravity flowing fuel--nothing with any kind of "release" mechanism.
3) I simply pack a good size funnel with a flexible gooseneck spout. I like this one:

I clicked on
@Laura link for a gas pump, above. There's a coupon for it, good till June29, you can get it for $7.50.
And yeah, the Ford-provided funnel is a joke. Please, Lord, protect us from regulators and "safety engineers!"