You don’t need to open the bleed upstairs, just force the water through til no bubbles out the valve downstairs.
Nick my man, Home Boy, Big Jim doesn’t want to FILL the system kind sir He wants to empty it for servicing and relocation of copper heating tubing
Getting Air bubbles OUT is great as you do not want air in the system other then in the expansion tank unless it is a diaphragm type.
The old ball valve below the hose bib trick aint going to work here to get bubbles out of a draining system.
You got to think like a Lawyer VERY methodical and exact not like a P&H Fraud .
Personally I think the majority of single family home owners are very capable of doing their own heating as they have the same qualifications as a P&H contractor if you think about it.
I’LL Bet Big Jim does not have an underslab failure that we read about HUH Nick? know why?
Because Jim cares and reads and wants to do it right