Isn't this all extremely complex?
Not really, there are two components - one, fuel preparation... on the face of it, it is about getting the particles from 80-100um to 2-3um - however there will be cleaning. Also, since there is cavitation, there may be heavy electrons formed and also potentially hydrogen species ad/absorbed into the processed powders.

Maybe MFMP will show a drawing of the reactor?
Will look to do this

Is there a procedure to prepare the fuel?
Detailed essentially in the sound cloud interview and videos above.

How exactly the reactor is started and stopped?
The 1MHz frequency generator is switched on or off and applied via MOSFET driver to 1-8 cores depending on desired power output.

Are any further initial steps needed to start?
As said above, a vacuum is initially applied.