I picked up a can of Duplicolor self etching primer from Napa tonight for $5.83. They only had one can, but that will be plenty for now. I primed the firewall parts surfaces that will be contacting the firewall or back to back with other parts. Everything else will be left bare for now until I paint the inside of the cockpit when the fuselage is done. Hopefully, I will get the firewall all riveted up over the weekend.