Mix a a small amount of epoxy and brush it on. 2 coats minimum.

But I'd remove the etching primer first. They do not play well under epoxy because the acid (the etch) in etching primers hinders the cure of the epoxy resins. Bad juju.
Idealy you have two or three coats of epoxy primer over any bare metal then your filler and high build coats if used with a reduced epoxy sealer coat on top just prior to paint.
Filler, poly primers/high build and the like absorb moisture and do not seal out water.
Epoxy primers do not absorb moisture and Do seal out water.


Give me ambiguity
or give me something else