barnfind
Old Man with a Hat
As Dave stated a wash primer first on bare metal inside and out as best you can. Wash primers are water-thin coatings of phosphoric acid insolutions of vinyl butyal resin, alcohol, and other ingredients.They are very low in solids with almost no filling qualities.Their functions are to passivate the surface, temporarilyprovide corrosion resistance, and provide an adhesive basefor the next coating, such as a urethane or epoxy primer.Wash primers do not require sanding and have high corrosionprotection qualities. Some have a very small recoat timeframe that must be considered when painting.
Remove lead like Alan has shown, neutralize any rust in the seam with some sort of phosphoric acid then paint the seam with a decent paint not primer then use a all metal type of epoxy filler to smooth seam, plastic filler for final finish leveling. This is what I have done in the past. I am not a professional body man so don't take it as gospel.