Best way to flush engine after rocker arm failure?

Once things are back together it might not be a bad idea to do a test run with the valve covers off and some makeshift splash shields to keep oil from dripping down the outside of the heads. Run it at idle and give it some light revs, hold it at 2500 RPM or so for a while, and watch the rocker shafts bolts closely. Also once fully torqued and before running the engine mark the bolt heads with a paint pen so it's very easy to see if any start turning.

If they still come loose, maybe try safety wire...
Kidding of course LOL