"I took a small funnel and shoved a vinyl tube with 3/8" ID on the end of
it.
> The tube was about 24" long."

I've done it this way too, but jacked the van up on that side to let the
tire sag. It creates more space and vertical, rather than lateral flow. It's
very, very slow, especially when cold.

I prefer to jack the van up and use a small pump that goes into a quart
container with a small length of transparent hose into the fill hole. I can
"stop" when it's just below the fill hole that way, easier than when filling
with a funnel. I find it also a lot faster than gravity. Just my preference.

bob