I'm at this too...
... and I did a bit of research. I did not want to do the whole keel the first year. So I got an angle grinder, took it down to shiny metal in the rsuted areas, and painted a coat of clear epoxy (within an hour of sanding). I used the West System stuff. Then I mixed some light fairing to he epoxy and applied a coat while the first coat was fully cured. I sanded and apply more coats wheer necessary then painted with anti fouling. On the second year there was no rust. It is not a final solution (nothing is) but good enough from me!!!
