For filling the water tank on a Westy:  Camping World (and I'm sure
other RV supply sources) sells a screw on adapter that goes onto the end
of a garden hose.  It had a shutoff valve on it, and terminates in a
foot long flexible clear plastic section that fits into the Westy filler
just perfect, either model (worked fine on old style on my '85, works
fine on the new style on my '90). Note of caution:  There are two sizes
available, one with the filler about 3/4" in diameter, the other
smaller, about 1/2".  Get the smaller one.  The larger, even though it
works, blocks the venting of the air from the tank as the water fills,
not completely, but just enough to slow thing down.  The smaller
diameter filler works better.
While on this subject, I have found that the small collapsible 'flat'
hoses that are sold at the RV stores work great for the occasional
hookup or fill up in a campground, but take up virtually no room in the
van when not in use.  Much more convenient than standard garden hose.