This is our proprietary FA Subaru Oil Pump Primer (OPP). This was created by a friend of mine because he was tired of having to take the messy / long route of priming by hand or worse... risking damage to that newly reassembled Subie.
How does this work? Simply attach the 3/8 drive socket to your impact, drill, or similar, and give her a gentle whirl. You won't need high torque, just a few quick zips and the oil is flowing.
*Demo video coming soon