Let me answer this part for you:
"but then absolutely nothing shows on the Transactions for that Customer:Job"
Because you have no transaction in the name of that Customer:Job = No sales event, at this point.
A Check to pay the electrician, has the Name of the Electrician = source Name. The Job Details are on the items tab, and you allocate to as many jobs as you are paying them for, on this one purchase. These are Target Names.
You have no customer Transaction, But you have Job Costs as expenditures, from those details.
All of this is in that attachment I provide, including Images.