I did months and months of research on here and landed on this solution. So far, no issues...
• Cleaned walls with TSP and rinsed off. Make sure to clean all the way to the edge...this cleaning process is absolutely the most important step.
• Primed with XIM adhesion promoter primer
• Painted with Duration latex paint from Sherwin Williams (made to be easy to clean, and it is)
That's it. If you have the whole trailer gutted, and you are feeling brave, I'd rent a paint spray and spray it on. Gives an nice uniform, factory look.
Also, some have said to "scuff" the walls, I did not. Primer and paint have stuck fine.