I would venture to say the water washed out some of the trapped brake dust that was causing the squeek? I would recommend pulling the drums off just to be sure though
Get some brake cleaner and go to town on the inside of the drums. All the buildup there is causing your squealing.I don't think I need to adjust it, since it's auto adjusting (drive in reverse, then pump the handbrake a few times),
But it does give a good idea on how to remove the wheel hub, and see inside.
I'm more thinking if something needs lubricating?
The front brakes were squeaking (according to what I read), because of the metal springs holding the brake pads in place.
If I had known, I could have just purchased the brake pad hardware (springs), and installed those, and use the stock brake pads.