I think that doing the part of a pre-flight which envolves pulling the tail down with a passenger onboard in VERY Foolish, and I have to add that I hope that was mentioned in jest!
You are right about the filling of the trgb it is generally done with the aircraft on a flat surface, and similarly with the mrgb. My engineers and pilots all check both levels with the aircraft on flat ground. (Well, as flat as is possible!)
Another thing which I would say to all pilots, just for safety's sake, when doing the 'tail pully downy' bit do it with the ground handling wheels ON!!!
It gives the tailcone a fighting chance of not being crinkled!
Fly safe, and remember,
Some days you are the statue and some days you are the Pigeon!!!