Hi Bennybob,
I put considerable effort into developing a method which would allow me to work on the coach sides on the flat then simply fit them in place. Then take them on and off again as many times as I want without any difficulty. Clean the insides, move the passengers about, that sort of thing.
The simple answer is magnets, have a read of the blog two back ;
If you have look through the blog as a whole you will see that it is a continuing theme for me. Causes a wry smile and I do tend to waffle on a bit but there is method in my madness. I try to make models which are easily maintained, probably as a result of spending lifetime trying to sort out things which are a nightmare to maintain due to bad design.
So I have buildings and stock with the roofs held on by magnets. Electrical sub assemblies which slot into place. Signals which plug in and couple to the servos magnetically. Compensation beams with screw adjustment for ride height. Baseboards that lift up like a car bonnet so I can get at the gubbins underneath easily. The whole layout on castors. All for ease of maintenance.
If I needed to decorate or do serious work to the room I could remove all the delicate stuff and wheel the whole layout into a different room in a few hours.
As I said I waffle on a bit, but there some useful ideas in there.