After having thought about it more, I think the basic requirements are
1. remove filter, as it allows to suck out reservoir more and the return line opening will be exposed,
2. most important: close return line opening. I thought a plastic champagne cork might work (or another cork wrapped to proper thickness), a fitting metal plug would be even better,
3. put return hose into 2 quart milk container and tape hose to it and container to ac hose or something nearby.
4. Then, with left hand over reservoir and bottle of fluid in right hand have someone start the car and then pour fluid. If I'm not mistaken, the whole system takes about 1.4 quarts but you don't need to fill it completely. But combining 2 quarts in one container sounds like a good idea.
5. The person who started the car will also turn the steering wheel 2 times end to end while 1.5 quarts go through the system. Then have the engine cut.
6. Connect hose to reservoir, install filter and fill.
7. Final bleeding.
If somebody knows the plug size and where to get it, that would be appreciated.