I have used a home made tank (out of pipe) that I thread into where the oil pressure sensor goes and hit it with 30-40 lbs of air after filling it with oil, being careful not to run it dry. I add all of my oil into the engine this way when it is new if the pump can't be spun with a drill motor or I don't have an adapter to do so.

The machine shop that did the work on this last engine uses an old tank type of break bleeder to do the same thing and it gives them the ability to lift the tank so they can judge how much oil they have left.

89 Ext cab 22RE 5 speed
84 Ext cab 22R 5 speed
88 Mitsubishi Macro Cab 2.6 5 speed