You'll need to use a Windows 7 machine and the proper LG USB Driver (first post of this message) and change it to the COM41.
Do a BOARD DL and when the screen comes up and tells you to not touch it, ignore and press OK. Then press the power button and at the same type touch the "Normal +power". It should reboot and everything should be fine
Should I use windows 7 32 bit or is it fine with 64 bit?
Will I need a .TOT file and a DLL for my model ( D855P 16gb ) or can I use a KDZ file?
EDIT: ok so I tried it, but flash tool failed to get model information from the phone.
were you in download mode? I can't get to download mode here.