My method is to put epoxy primer down when I have the body work close. I prefer it as the base coat.
Then I start blocking with guide coat and using mud where needed and topping it with high-build primer as
the work gets closer and closer. Lastly, a little glaze if needed and a good coat of sealer just before color.
It's not right or wrong, it's just the way I do body & paint.
You are on the right track and you want the right coating on that bare metal. I'm sure you will get other
input which may vary. A lot depends on your paint vendor and your budget as well.
Best of luck as you proceed!