I've seen someone take an old clutch disk and bolt on a bicycle front sprocket and then use collar to secure the disk on the spindle to make sure it doesn't slide.

From there, they attached that chain to drive sprocket off of an old scooter. Using a wire off the output shaft to measure rpm, they revved the thing up.

that worked excellently, and if you have a pressure guage, you'll know if you're good to go.

Getting the transmission up to 1500rpm helps.

You could attach a chain to just about anything you can crank to spin up the transmission....

I would first take the pan off the OD, clean the screen and assess the fluid and any metal flakes stuck onto the magnet that's adhered onto the inside of the od pan.

J