Have fun with it..
I have used it before in a profesional auto restoration shop. Some places it is a good idea, but it can make a mess with the MIG welder popping and spitting. If you first scrape the visible stuff out of a plug weld hole it helps some.
It's a nightmare with the TIG welder, you better enjoy grinding tungsten.

Some brands are worse than others when it comes to welding over it, and the harder ones to weld around are probably the better at not rusting. The two I used were made by Wurth http://www.wurthusa.com/project/en/leftnavi/catalog/product.php?path=04.0241.jpg and 3M http://multimedia.mmm.com/mws/mediawebserver.dyn?6666660Zjcf6lVs6EVs66SMj3COrrrrQ-

The Wurth brand was the most difficult, before to long the spray can had a new paper label, it read "Spray on weld contaminator, best when used liberally"

Grigg

•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
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"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-