Oil pump priming question
Most (?) will spin at 400-500 RPM loaded down in low speed mode (equal to 800-1000 engine RPM), and with cold oil, that ought to get many 10's of PSI of pressure. I use a Milwaukee corded 1/2" right angle drill (Milwaukee electrician's 'hole-shooter' LOL) running at 500-600 RPM, and with cold 10W30 oil it will hit the 72 psi relief valve limit.
One thing we have not mentioned IIRC, is that the oil pump could be shot.