I found many writeups on how to bleed/burp the cooling
system, but...

How do you purge all the antifreeze?

I just bought a 91 Westy and wanted to change the
antifreeze. To purge, I disconnected the radiator hoses,
opened the bleeder, captured the antifreeze, and
reconnected hoses. Then I disconnected one rear hose from
one plastic pipe.

This netted about 2 gallons of antifreeze instead of +4.5
gallons listed as capacity?

I wanted to get it running, so I flushed by putting a hose
in the pipe and ran water until it came out the only
detached hose. Then I added 50/50 coolant and now I'm where
I'm sure many others have ended up before me. ;-)

Did I end up with +2.5 gallons of water wherever the extra
coolant was? Or did I miss draining another loop?

How do I drain correctly next time, to capture +4.5 gallons
of old antifreeze?

Thanks, Matt