Pre oiling a /6. What method?

Remove the oil pressure sensor, install a (same thread) fitting you can adapt a hose to. Using a pressure pot (garden sprayer) or a squeezable bottle of the sorts filled with your favorite oil, connect the hose to the pressure pot or squeeze bottle and let-er-rip. I'm sure there will be other recommendations, but I've been using a pressure pot method for a long time with good results.
Norm