Filling the Crank with engine oil ?

I adapted my grease gun to the end spigot of the crank with pieces of tube and Jubilee clips until a decent pressure was felt as I was pumping it in and satisfied myself that all was as full as it was going to be. All this to be done as the last part of the rebuild to lessen the time for oil to drain away before actually starting the motor.
Some folks have adapted the rocker feed port for the same effect.

I've always just kicked over a few times.  The oil feed from pump to crankshaft is a very short distance and very small volume compared with the return distance, especially if a filter cartridge is added.

I just use an old trigger oilcan .Very little pressure is needed.

Just fill the oil tank and leave it for a week or so. The oil will gradually make its way through. Simples.

Adding to the practical moves here.......just before starting the engine for the first time.  Remove  both exhaust rocker covers and add (squirt inside) around a cupful of oil to each pushrod tunnel. This will help lubricate the cam followers, camshaft and also provide a small bath of oil for the pump so suck up and distribute to the rockers.  It all helps.

...Use assembly lube.  Keeps the mess inside.