I know it sounds crazy, but I do. It takes FOREVER !!! But everything here couples to everything else. Just like 1:1 scale !!! Isn't that actually the goal ???
For passenger trains, no need to go to that expense. Kato's work well together, crud even Rapidos can work fine for passenger trains as they usually stay coupled as a consist.
I did it to a new track cleaning car so I could pull it with the strongest engine. Of course turning around allow using lighter engines or pull more cars.
As named passenger trains were given the highest priority by the railroads because it was compulsory that these flagship consists arrived on time, head end reefers containing express freight parcels and in some cases mail were most commonly found on the Class I railroads' famous runs. Designed to transport whatever kind of product the Railway Express Agency was consigned to move, with their ice bunkers collapsed, refrigerated REA reefers that were commonly used for perishable goods shipments, were also suited for moving dry goods. In the late 1960s, following the demise of RPO cars, as many as three or four REA reefers could be found at the head end of streamliners and short passenger car consists. https://www.american-rails.com/equipment.html
The various Fast Mail trains of different roads often cut cars in and out at points plus carried passengers and they were a higher priority than the flagship passengers. Thus when I modeled them the headend cars all were MTs.