I have sand blasted some bad seams with one of those cheap little hose in the bucket blasters.
Worked pretty good for seams, as a matter of fact, you would want a small area blast ark.
after blasting, I use the POR 15 to seal the rust, sand it well with 180 grit wet or dry.
Then flexible seam sealer over the top of that.
Primer, paint, blending & you're good to go.
Doesn't replace a total paint job for sure
But takes care of the problem for a couple  of years. ( We'll call it remission ) ...
Of Course, the rust is in The Middle of the Seam Flanges.
And, Short of replacing a panel ( which I've done )
no matter what you do to the outside Or the inside
the rust is still in there.
But, Hey, When I'm sitting around the campfire in the forest,
I try not to obsess ( too much ) about it  ;o)

John C...

As always Mr. Phelps, The State Dept will Disavow any knowledge of you or your Mission Impossible Team :o)

-------------- Original message --------------
From: pickle vanagon <greenvanagon@GMAIL.COM>

> Has anybody used POR Patch as a seam sealer?
> http://www.imperialrestoration.com/products.php?category=8#18
>
> -Wes