Personally, I think there are much superior finishes to Cerakote these days. For an action, finishes such as nitride and DLC provide more lubricity, and add zero to very minimal thickness to any parts applied to. As mildot points out, applying cerakote to an action that's on the tighter side of tolerances can create issues in adverse conditions. My Defiance Rebel action with Cerakote would give me absolute h*ll in adverse/dusty and windy conditions.
If it was me, I would get the action treated with nitride or DLC, by a qualified and competent applicator. If DLC is not applied properly it can flake off and chip, and nitride is done at such high temps, that if not done properly can change the material properties of the material it's being applied to. Not an issue if either of these treatments are done by a reputable vendor, but can turn into a cautionary tale if you decide to cheap out.
Barrels I leave untreated, they are disposable and I don't see the cost being worth it. That doesn't mean you shouldn't coat yours, but if you shoot a lot and are shooting a cartridge that is hard on barrels, it's certainly worth a look at the economics to see if it makes sense.
If you have to go with Cerakote (for whatever reasons they may be), I would look at the new Cerakote Elite coatings. They are thinner and have more lubricity then the original formula.