I'm not sure how your pumps are plumbed, but with the 743's i have worked on, i primed my pump by filling the oil tank, then i had a helper put their heel on the lift pedal then pulled the lift cylinders out. This draws oil from the tank, through the pump(s) to the cylinder. I did that with both cylinders to get as much in as possible, then get them to push the pedal the other way, then push the ram sticks in. Then retract, just to get as much oil in as possible.
I don't know if that is an option for you or not, it may only prime your hydraulic pump.
When i started it, i made sure it wasn't long with the wheels off the ground, they didn't take long to start turning, so they had oil.