Hi-
With all this discussion of rust conversion products, thought I'd put 
some of my $.01 in.  Checked with auto paint stores.  They described 
two types of rust conversion products.  One type requires flushing 
with lots of water after a period of time.  The other type one applies 
thin and let dry and then paint over.
2 years ago I used the let-dry type and the rust is coming back in 
some places.  Other places I used the same stuff and it worked well. 
Probably my technique.  However the worst rust location I need to 
work on is in the vertical panel joints in my '80 Westi.  
Any proven techniques for this location?
-Jeff