If the fluid is REALLY bad... then something like a turkey baster should be used to evacuate the ugly stuff from the container, maybe even flush by filling a time or two and doing the same thing.. then putting good stuff in to start the bleeding...
Three years ago I did see an early 80's Buick that I would bet had the original fluid in it... it was BLACK...
I think the rule should read furthest, next furthest... because on some cars the routing is different to the rear..."as the crow flies the RR would be the furthest on left hand drive cars... but I have seen cars with the LR the furthest if you follow the tubes..