In the Sim, do it nice and methodical, just the way the Instructor briefs you.
In the burning, smoke filled aircraft, just remember to shut off those Start Levers before you issue the 'Evacuate' Command.
The rest of the items can be done, or not, and it will not matter too much.
Flap 15, so what?
Outflow valve half open, so what?
No power on the busses, so what?
One fire bottle discharged, so what?
Fuel shut off, Evacuation under way, ........enough.
We are talking human lives here, not the details of a checklist written in an office in Seattle.
btw, imho, the checklist written on the back cover of all QRHs should be the smoke removal drill, in great big letters. Can you imagine trying to find that buried in those horrible orange pages if the cockpit is filled with smoke?
Pax evac can go inside the cover!