Miror lock up is for different purpose, not for sensor cleaning purpose. I think you got confuse between the 2 terms.
Just look under main menu for "sensor Cleaning", when you chose it, it shoudl have a message said "turn off power after cleanning" or something like that...
It's not a hard process, but make sure you read the manual to make sure you know exactly what to do .
I've just ordered an Butterfly Artic frush too.. hope it'll work better than other methods