Fellow vanagon types 
pulling spark plugs from a hot aluminum head can cause the treads to come out with the plugs. for this reason I was told never pull plugs from hot heads warm ok hot never. There have been times when I have gotten away with it but the risk remains.  
bosch tells you not to use an anti seize compounds on spark plug threads and that the new Bosch plugs have a anti seize component already installed. I have been selling single port air cooled bug engines for use in Zambonis for many years most are converted to propane to improve in door air quality. The change to propane has some dramatic results including the fact that unless you use a anti seize compound on the plug threads you will need to helicoil every plug hole the first time you change the plugs. This is due to the extra heat from the propane fuel. most any compound will prevent damage and does not seem to insolate the plug to the point that the plug will not fire. Black oxide plugs such as AC Delco are not made to be run in aluminum heads as they weld themselves to the heads with ease. 
Torturing of new spark plugs according the Bosch automotive hand book is done by turning the plug until the gasket makes contact with the head and then turning the plug about 90 degrees. used plugs should need about 45 degrees turn after contact. I tyr to feel the gasket compress as I tighten the plug and yes I use anti seize on all plugs and I treat the new engines I build to a dose of anti seize on the spark plug threads before I ship them out.
Reading spark plugs is best done when the engine is shut off under load then read. once the engine has been allowed to idle the plug reading won't tell you much other than extreme problem like flooding or a to way to lean condition.
the vanagon heads (spark plugs) do see a fair amount of water when the vans are driven in the rain and snow moisture and other things can collect in the plug recess. because of this it would be a good idea to blow out the recess with compressed air after loosening the plug but before removing them. 
  
Bob     
http://www.bostonengine.com
all rights reserved