priming the oil pump

If you cannot get anywhere, I would verify that cam oil hole is lining up. Cam bearing, etc. Take a piece of similar, brass brazing rod, and insert it down the dry oil hole, so that it can go down through the block. Remove the plugs and GENTLY turn the engine with socket on the crank bolt. At some point the rod should be able to drop into the cam. Be certain you don't get wrench happy and shear it off.

Years ago, someone on here had posted the crank degrees at which the two sides line up, but I don't remember, and never have done it that way.

Your drill should be laboring very heavily if pressure is building. You should be able to tell by feel.