<< I don't know what Rust Mort is, but it and naval

jelly are similar. >>

The problem with either of these products is that, as stated in bold type,
they are supposed to be rinsed with H2O prior to priming.  Now, that can be a
problem on a seam which wicks in water like a sponge.  Once the moisture is in
the seam how do you dry it out completely?  A shot from the good old blow gun?
That may produce the opposite effect than what is desired and drive the water
farther into the seam.  An old timer machinist once told me that he could
tell how good a hand was by just watching him clean a machine after a job.  If
the guy used a blow gun to clear away the swarf, he was a hack because he was
not blowing the stuff off, he was blowing it in.

Plug in the heat gun, Homer.

George