Soak the parkerized parts in acetone to pull the oils out, and the coating will bond without problems to the parkerized surfaces.

Where you may run into some problems is if the under surfaces are not a true parkerizing.  On the below Sig, the frame is anodized and Duracoat bonds without problems.  The slide has a good parkerizing coating, and here too, the Duracoat bonded without problems.  The hammer, and a few other parts where oxidized, and since this process doesn't produce a surface that will allow the Duracoat to bond well, they where blasted, parkerized, then coated.  As for my reasoning to use Duracoat over something like Gun coat, Duracoat does not require the parts to be baked, But the down side to Duracoat is that it takes about three weeks before the coating has total hardened.

Also, this one is a huge one, when you coat the parts, sear contact areas should not be coated, or it they are over sprayed, make sure to remove the coating before it is baked or cures.



And since you are coating a 1911,