I think this is an easy way to prime and bleed the throttle line, hope it helps others.
1 & 2) Get a hand pump that screws onto a quart of oil. I'm using the same pump I use to fill the lower unit of my I/O on the boat because with each pump/downstroke no air bubbles are pumped into the line. Configure clear tubing so you can screw a fitting into the tee that is near the carb throttle cylinder and the other end of the tube goes to the pump.
3) Remove the bleed screw on the handle. Squeeze the handle to full throttle and hold it. I like to remove the handle and work with the cylinder, its easier to see a leak when the bleed screw is installed later on.
4) Slowly pump the oil into the system. Air & oil will bleed out the handle. Keep the bleed hole pointing down into a rag or container, it will "gyser".
5) Keep pumping until no air bubbles are being pumped out and you know the line is full of oil.
6) Keep holding the handle at full throttle and screw in the bleed screw. Then slowly release the throttle while pumping the oil to fill the front side of the throttle cylinder as it retracts.
7) Check for bleed screw leaks (or other leaks) by applying some pump pressure. Remove the pump fitting. The entire throttle line should be filled with oil.
8) Install your check valve and reservoir assembly and you should be good to go.
9) If you use a plug make sure the cavity is filled. I found that the air in the cavity would make its way into the line.
