Years ago (decades, actually) I got a galv funnel with little ears that lock into the filler neck the way the cap does, so the funnel doesn't wobble around when you're pouring. It also has a fine brass screen in the bottom. Haven't seen one lately, but haven't been looking either. I think I got it at Agway. Still there's sometimes a bit of fuel on the hood after.
Actually the hard part is not fueling until I'm down more than halfway on the guage, as there's no way to tell the tank's full until just as it overflows. Probably the rear tanks are better that way. Below half on the guage it'll take 5 gallons OK. Some kind of storage tank would be good, but I just don't use enough. Maybe when I retire...
Jim