I understand that cars cannot be coupled on curves less than some radius. But on smaller layouts, much of the trackwork is curved and there may only be a few locations to have straight sections near passing sidings allowing coupling. What are there locations?
my guesses are:
just beyond the diverging legs of the switches, allowing cars to be uncoupled on either branch of the siding
on the non-diverging leg of the switches, at least several cars away from the switches/siding
somewhere in the middle of each branch of the passing siding
It’s the same for coupling and uncoupling. For hands-off (un)coupling both pieces of equipment will have to be on the same piece of “straight”. Five times the length of your longest car involved should be the minimum radius. A 60 foot car will need at least a 41" radius: on a small layout?
So, most people are using some sort of a device (e.g. a wooden stick) to aid the process manually.
To reach over scenery or trains, between you and the action, will require some thoughts while planning your layout.