Finding the error
I am slightly surprised that people are suprised you can make this kind of error :-) Perhaps I am unusually dozy, but there are many "automatic motor actions" that I interchange on a regular basis. I have certainly, for example, picked up the coffee pot when I was looking for the frying pan, turned on the car windshield wipers when I meant to turn on the headlights, and to be more on topic, turned on the aircraft fuel boost pumps when I meant to turn on the ignitors.
The key is in identifying the error in the chain. For example, if the checklist calls for "igniters on", I reach over and flick a couple of switches. If the other pilot says - "Hey, the igniters are not on" - then we might go ahead and look again, and switch them on. BUT the other importnant task is to go back and determine - what the heck DID we turn on last time?
The same opportunity was present in the park brake incident. The PF called for the flaps, and PNF did an action. On later review, the PF noticed that the flaps were not set, and called for flaps again. The PNF selected flaps. The missed opportunity was to say - "Since it wasn't the flaps, I wonder what you did LAST time I called for flaps...". That may have got some much needed attention back inside the cockpit for a moment or two, and avoided an embarrassing rubber stripe down the runway.
This seems like an excellent CRM learning example.