Painting advice

I just recently finished painting the exterior of my Dart. It was the first time I had ever painted a car and I learned a lot. I’m curious with how to go about painting the inside of a car. Is the prep of the metal on the inside as important as the outside? Just thinking about tight spots like between the rear quarter panels and the trunk drop downs and the floor of the car. What’s the best way and how do you prep these areas for primer and paint? Is it the same as the exterior? Thank you in advance.

wanted to add this, a lot of the panels on the back including the trunk floor the quarter panels the tail panel are all new and have the black EDP coding on them. Does this need to be removed?
the edp coat stays on acts like a sealer just scuff it when it comes to the interior floor & trunk floor I just paint them with a brush no one sees them