My 1992 ford explorer

[DaveWM]

I thought I should replace the brake fluid, started by sucking out old (1/2 way) and replacing new, did that a few times until it was reasonable clean.

tried bleeding rears, did not want to flow, I got some out, no air, but way too hard.

fronts bleeding went as it should.

Did some research, seems lots of folks have issues getting rears done.
not sure if its the RAB unit but I assume so.
Not sure if it needs some speacial device to plug in (read that somewhere) or if its just bad from years of yuck fluid (rust).

the rears had VERY little wear so I wonder if they are working at all. Of course I did replace the shoes a couple years ago, and do not drive the car much and I know how to drive so brake wear is low in general.