paint over epoxy or epoxy over paint ???

I just started a 5x10 gambrel barn trailer. Yep nothin' as aerodynamic as a barn
My question is over bare t-111 siding should I epoxy 1st then rough sand and paint or should I paint then overseal with epoxy.
I relied on marine spar varnish on "Chubby and he is looking pretty sad so a major sand and fill and paint is in his future too but I am hopeing to take "Barn to be wild" to the tri state gathering the end of July so I gotta hustle. I would like to do this paint job only once. I intend to use an oil base barn red paint unless that is a problem.

My question is over bare t-111 siding should I epoxy 1st then rough sand and paint or should I paint then overseal with epoxy.
I relied on marine spar varnish on "Chubby and he is looking pretty sad so a major sand and fill and paint is in his future too but I am hopeing to take "Barn to be wild" to the tri state gathering the end of July so I gotta hustle. I would like to do this paint job only once. I intend to use an oil base barn red paint unless that is a problem.