While the rams don't care, the pump does.

I can't find my paperwork, but the guy that rebuilt my pump specified filling only in one instance. Filling at the wrong time blows out some pump seal, or over fills the resevior and blows out that seal.

Regardless, the only way to air it out is to run it up and down a bunch. Give it a rest inbetween otherwise it starts to smoke.

A fan on it might not hurt. It isn't meant to do a lot of rapid cycles.

Then pull the plug and top it off. Really wish I could remember. I seem to recall filling it with the top down, but again don't remember for sure.