I had good luck with POR20 hi heat coatings until moving on the stainless steel components.
It is all in the prep work.
I sprayed the product in very light coats after all the chemical degreasers and preps.
I did this on the most humide days in the summer time as the product cures and hardens�with moisture.
It would hold up on 75% of the exhaust very well for about 2 years.
I brushed any touchups needed.
These exhaust systems were used to begin with and saw year round driving in salty winter conditions.

I have had very good luck properly wrapping steel exhaust systems.
Two layers of wrap, cross laminate the windings and use DEI silcone sealant on the wrap to keep all moisture out. I used 1 inch or 1.5 inch first, than 2 inch wide over top. It comes in colors.
Wrap the system tightly and remove, wet the wrap to allow it to flex into all the tight bends, run the engine to dry or use a heat gun to get the water out. I would wait until the next day before going with the second layer.
Stainless ties are a must if you want it to stay put.
I like the look of a wrapped exhaust.

You won't believe how much heat goes out the tailpipe and not into the engine compartment.

Hope this helps

dylan

________________________________
From: Zoltan <thewestyman@GMAIL.COM>
To: vanagon@GERRY.VANAGON.COM
Sent: Fri, October 23, 2009 3:02:07 PM
Subject: Rusty exhaust. Paint?

Hi to all,
I was wondering if anyone knows of a kind of paint that would help a rusty exhaust to be preserved and look better.
Zoltan