Hello Ron:

The plan as shown is not making use of isolators and it only has one feeder. That plan can run off one transformer.

In order to do a 2-train operation, you need a second 8590 feeder track and isolators ... the second 8590 feeder is installed in place of one 8500 on the outer loop. The 8954 isolating joiners would then be placed in-between any two of the 8568-8521 or 8569-8521 junctions.

There is no wiring diagram nor instruction as it is painfully simple. An 8590 accepts a brown wire and a red wire. If you orient both 8590's in the same direction, you cannot miss the wires. Red - brown from a Marklin transformer plug into same orientation of each 8590.

To remove joiners from turnouts can be tricky and expensive if you mess up. So, be careful. Peel back the plastic sleepers (ties) and then pull the metal joiner out. Replace with a plastic Marklin 8954 joiner.

I also saw this post on several other forums where you were concerned with the locos shorting out crossing the isolator. Not going to happen. If you are one truck on inner loop one truck on outer loop, you can have short bursts of extra current, but it won't kill the loco unless you are at high speeds. Run your locos at crawling, prototypical speeds and it becomes a fun game of matching speeds as you go from inner loop to outer loop.

Here is one example of an isolated loop track setup on the Noch Tessin layout; inner loop and outer loop are separate circuits and I show a train jumping from inner to outer ... yes, trains were running fast, but it was to speed up the runs around the layout and shorten the video length: