90 K1500 4x4 10" rear brakes.
(the leading/trailing style with the adjuster at the top)

replaced the rear axle seals yesterday (leaking bad bad bad) and the
rear shoes.

Brakes were working before - just crappily because of all the grease on
them.

Now... the brake light is on, and the pedal pretty much goes to the
floor - not quite as soft as if there was air in there, but pretty darn
soft.

It would appear BOTH rear wheel cylinders are seeping. The only thing I
did as far as the hydraulics was to push the pistons back into the
cylinders so we could get the new shoes on. Is it possible that there
was a bit of corrosion in there that caused my leak? And/or is it
likely I did something wrong with the self adjusters and the leak is
actually just seepage from doing that and it's not really a leak? I
tried bleeding the rear brakes and they seem fine.

The truck has rear wheel abs.

I'm going to replace the wheel cylinders because I'm assuming they're
fubared, but I'm wondering if there's some other trick/something I did
wrong.

Also, the park brake cable is currently not connected - the whole thing
was rusted solid so we pulled it all out and I'll be getting new cables.
The park brake switch was disconnected.

Ray