Hi, which year? Big difference between older chrome bumper an
later plastic one.

anyway, for both i use Mar-Hyde Black Satin for everything that is black
on a Vanagon. It's just perfect bringing back the original black.

http://www.benplace.com/85westy/taupe96.jpg
http://www.benplace.com/85westy/taupe95.jpg
http://www.benplace.com/85westy/taupe124.jpg

this is also what i have on my chrome bumper, but, i use an "adhesion"
(i'm not sure about the right word in english) primer. It's basicaly a
glue in between paint and bumper.

It holding pretty good after 27K miles, but of course i had some stone
chip in the front and i had to redo this one.

Ben
http://www.benplace.com/