Cowl (sealing)

Im pretty well versed on cowl rot. leaves and crap and years of water taking their toll. But now I have a 65 with no visible holes or rot! amazing. However, I've just went through the vacuum, scaping chore to clean it out. even the inspection camera shows good metal!

However....I want to seal it somehow. I'd like to prevent further rot and IF there is a pinhole or two....seal it now!
WITHOUT cutting it open....how would you suggest sealing the surface? I was thinking of pouring "red Kote" tank sealer to seal the floor. But that would only seal the bottom.....

Is there a wand spray that would work spraying a surface sealer? POR thinned maybe? undercoat gun and wand???????

Here is some "fun" picts of a previous cowl I fixed. Lots of fun on this one. I DONT want to do a job like this again!