I need to change the wheel cylinders on the rear andwant to know which way to turn the adjusting screw wheel to back off the shoes. I'm starting with the driver's side. Should I pry it up or down?

eather side will be the same.
If you are going through the backing plate, tip of your adjusting tool will turn the adjuster counter clockwise. Going through the front of the drum, (some have this hole ) Your still turning the adjuster counter clockwise.
first you need a long small screwdriver or a coat hanger to take pressure off the adjuster from the selfadjusting swing arm. It rides in the threads of the adjuster and you wont be able to turn it the right way if it is toutching.
You release this by pushing straight in on the arm while turning the selfadjuster.
When you put this back together, make sure your emergency brake is all the way released. You take this adjustment out by loosining the adjusting nut where the two rear e-brake cables meet the main cable under the center or side of the vehical. This will assure your peddel will be right up there after you have blead the system.