I am not a big fan of epoxy primer so been a long time. I think you will be fine with what you are doing. You should make sure that you get everything as smooth as you can, like no ruff edges on what little paint you leave behind. Looks like the car has been painted over before so get that newer paint off the car. If you can get all the body work done before you prime in 80 grit or about, you will use less primer and less hand blocking in the end. Lots of primer and paint is not good in what I see through out the years.