Frame cleaning and painting

[Mrphoto]

So I started a little the other day on the cleaning of my frame.

My question, and this will NOT be a show truck or even a daily driver, is how clean do i have to get the frame?

I mean, glistening shiny metal or mostly metal? Do i have to get any deeper rust spots all the way out or if I plan on a simple POR 15 job or similar....

I know preparation is key and do the marine clean degrease, then the metal etching primer....etc etc

But how clean must the frame be? (see picture)
Also, how do you get the inside of the frame good?

thanks!