I always thought the simplest way to remove difficult-to-remove pedals was to use a block of wood, roughly the same height as the BB. Start on the DS by turning the crank until the arm is level and towards the rear. Set the block of wood under the crankarm at the pedal hole, engage the pedal wrench (or the 8mm allen), and push down. On the NDS, turn the crank to the rear and put the block under the crankarm at the pedal hole. Again, engage the wrench or the allen, and push down.
To tighten, just rotate the crankarms to the front, engage the wrench, and push down again. No need to try and hold the opposite crankarm this way - let leverage help.
I prefer not to remove pedals using the workstand - I'm leery of applying excessive torque to the frame tubes. By leaving the bike on the floor, it's really no different than a hard acceleration.
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Dale, NL4T