I think I'm going to opt for filling from the bleeders until I see fluid
just starting to appear around the shaft opening (A&P pumping, me
watching). 

Lee,

 

As I said in another response, fill from the bleeder valve until overflow, then drain some at the bleeder.  If you have original design adjustable rudder pedals, the bolts could be removed (if they go into nutplates) and the rudder pedals moved far enough aft to access the cylinders.

 

I think you need a mechanic with longer arms - we have several at ARR and they are cheaply paid with bananas.