I was rebuilding quite a few B18 and B20 engines a few years ago (still waiting for the B21 and 23's to wear out.....) so I made a pump priming shaft. I took an old pump driveshaft and pressed the gear off, and then welded a 3 inch 5/16 bolt to the upper end. I insert this into the oil pump before installing the usual driveshaft, and turn it ccw with a 3/8 speed handle with a 1/2 inch socket on it. Takes a few seconds to fill the filter, and then you can see the oil oozing out of the rocker arms. Works great, don't even need the reversing drill.