Over-revving the FW 190 D9 1945

[Derda508]

Sorry if I join here with a 'noobish' question, because I don´t fly these birds too often.
I tried to find out in the manuals, but could not find an answer. I remember that somebody in the thread linked above, once mentioned something like: "I turn on MW50 before engine start and then don´t touch it again." I also remember to have read that it should be turned on before you start the engine, because it only kicks in when you go full throttle. (which would make its use impossible for airstart missions). As far as I understand you talk here about turning MW50 on during flight. What´s the correct way?
And how can you override the Kommandogerät with manual prop pitch? If I try to do this in German planes just nothing happens.

Best,

DerDa