Get a peice of hard tubing that is slightly smaller than the I.D. of the
radiator air bleed bolt hole.  Available in the Northwest at True Value
Hardware or other sources.  Bend it into an S-shape.  Attach a funnel type
device and pour some coolant into the device with the hard tubing inside the
treaded hole where the air bleed screw sits..  The S-curve in the hard
tubing between the funnel and the end of the tubing will support the funnel
device.  I do this when the motor is off, usually after driving my van and
with the nose up a bit.  It would probably be smart to turn on your heaters
as you approach your 'bleeding-site"...
   Pour about a cup of coolant into the funnel and watch the air come
bubbling out of the rad.  Repeat.  When you get a solid stream of liquid,
you are done (for this time)..I do this drill a few times, until I get no
more bubbling when I add coolant.  I keep my dorky-device in the van for
road emergencies and I usually do a "pre-trip" air-bleed procedure.  Takes
me about 2 mins to remove/bleed/replace.
  Wonder why VW made the bleed screw so hard to get to when it gets used so
often and can be the cause of so many problems with a Vanagon..
  Don Hanson