The pump has no way of knowing whether half or overfull. As long as level never gets low enough to suck more air you should be fine. The pump will get noticeably louder when it eats air.
Lots of people have trouble and whatever trick they are working at the time is the supposed cure. The point is that air can really get chucked in there and the ONLY WAY it will EVER bleed is for all fluid to get back up into pump to be able to release its' air since air is trapped everywhere else in the system and cannot get out.
If you have more than enough fluid to fill it open and ready to go you can get someone to start car, run rack one way and then other, and you filling pump as fast as it eats. Done correctly it fills instantly with no air at all and no bleeding to be done. I do it all the time but you have to be quick about it.
I have jacked car up but actually better not to since car weight makes the torsion valve in rack open more to bleed more completely and faster. No load on that valve with car in the air..............