Do I just connect from tank to tank, ...

Sure, just turn the 500 gallon tank upside down first, so you get liquid
out, like you did refilling disposables from an upside-down 20 lb'er.

Expect cryogenic, flammable liquid to spew in your face, blinding you, and
instantly frostbiting your skin, just before the massive explosion and fire
that ends your life in a blood-curdling cry of gurgled horror, with your
family and neighbors watching your staggering death-walk across the lawn as
your burned lungs starve you of oxygen and you collapse.

Other than that, yep, it's just not "all that much different other than the
amounts".