Gerahead's 71 Dart

I am trying to put together a strategy to getting the car repainted in a different color. What do you guys do to get the trunk ready for a re-colorization? The trunk can become a repository for any number of coatings that can cause issures with paint adhesion and I don't want to have to do this more than once. I have power washed it with a water soluble cleaner, what else should I consider for making sure it is good to go? Thanks for the help.