We had this situation during our rebuild of a Christen Eagle a few years ago - this is what we did.
Prior to putting the engine to 'bed', we ran the engine up to temp, dropped the oil, put fresh oil in and ran it again.
Then, once cool, we opened every port, plughole etc and emptied a whole tin of Boeshield T-9 into it.
After that the engine stayed static - NO TURNING, occasional re treatment down the pushrods and onto the valves.
As that, the engine sat for nearly 2 years.
Prior to first start, we got an old battery, hooked it up, took all the plugs out and put rag into the lower holes to catch the stuff coming out. We then turned the engine on the starter for 15 seconds at a time, leaving time between each starter run for it to cool - total turning 1 minute. During this period, the oil pressure came up which showed that oil was getting everywhere.
Clean up, refit the plugs, new battery, cowls on.......................... Started on the 3rd blade and ran as sweet as a sweet thing !
Treated it as a new breakin and gave it some beans for the first couple of hours, dropped the oil then carried on as normal