There are lots of packages with which the drawing can be created. For this one, I used a simple image editing program (Paint Shop Pro), but for most of my work, I use Visio Professional. It has electronics templates that would make the drawing even more compliant with trade standards. I didn't think this circuit was complicated enough to warrant that. The images embedded in the drawing are reduced copies of the product marketing images.

Just sketch it out on paper to get the connections and organization figured out then draw it in the program. This is the final drawing; there were three or four versions done before I got it to this stage.

For example I had forgotten that the circuit breaker belonged close to the battery; I originally had two primary leads going to the two fuse panels and opted instead to use one and daisy-chain the power from the unswitched panel to the terminal on the relay of the second, saving me running two wires, and using only one circuit breaker to manage both. Of course this puts the total power allowance at half the capacity of the fuse panels (gated by the circuit breaker) but since I don't have any heavy draws, this isn't a problem and keeps me from overloading the panels later.