Ok, yes Bosch, Delphi, Frank Massey and James Dillon do courses as do others.
Yes I have done all Bosch diesel courses, some 2 or 3 times over the years as they do evolve.
Spent lots of time at Delphi when doing foundation degree course in diesel technology
Have been to ADS (Frank Massey) and discovered a completely different approach to diagnostics.
James Dillon, not been to any of his as yet.

Been in diesels since 12 years old and still say that we will all need to specialise in areas of technology (or at least my brain is not capable of covering all systems on all vehicles).

Where do I start when a vehicle arrives?
Assessment of the vehicle, is it worth repairing and do I want to work on it?
Where has it been before it has arrived at my door, and what has been carried out?
(use this as a guide and not as fact and also check over this work)
We all have 5 senses if we are lucky, use them.
Look at the whole vehicle.
Listen to the vehicle.
Smell the vehicle.
Touch and taste is also bought into it (more on that later).

Do I need to plug in a serial tool now?

If required take UP FRONT PAYMENT for parts before fitment.

Use ONLY KNOWN QUALITY COMPONENTS.

(May add to this later.)