Clean slate on roof rails

[Southbound]

I just welding on new metal to the roof rails. The rail junction is spot welded so the only seam, and thus most likely rust spot, is between the roof skin lip and the rain gutter. I think Cruisers came with some kind of seam seal in that spot but I'm wondering if modern technology offers a better alternative. Should i put some POR15 in there first and then seam sealer, or regular primer, then POR15, then seam sealer, or whale blubber oil and a prayer? Maybe you have some better ideas? I never, ever...ever! want to deal with roof rail rust again!

Thanks!

 

[PAFJ]

I use this stuff here
has worked great so far.