Painting an old home circa 1858. Painted in oil. This home is primed with an oil base primer "Alkyd". This primmer stabilizes and allows finish paint to be latex. If the previous oil paint is not neutralized the latex will NOT stick.
Scrape, wash (by hand with dish soap the best), check scraping after wash. Prime and calk as needed (best to put primer over calk) Also extra wear and tear and heavy pealing may be double and or triple coated.