When I built my Fusion 1911, I went with Norrels Moly Resin. In reading the instructions for best adhesion he recommended, sand blasting, then Parkerizing and then coating with the Moly Resin.
I degreased with Dawn dish soap and super hot water. Rinsed in hot water and then parkerized. Everything got oil bathed after coming out of the parkerizing solution to neutralize the oxidation process. Then it was back into dish soap and hot water rinse and then placed in an oven to dry thoroughly before applying the coating with an airbrush. Then back into the oven to bake.
This finish has held up very well.
I think you should get good results with Duracoat as long as the prep is done right and the finish is fully cured.