This is old as dirt, but put a rubber end on the wrench that you use, so it doesn't leave marks.
The Wii U has lots of keys: its OTP is 8 times the size of the Wii OTP (1KB in 8 banks of 128 bytes, instead of a single bank of 128 bytes). Incidentally, bank 0 is the vWii bank (and all the other...