would it be better to have switch machineswired to a seperate bus wire along with some other acc. i am wiring about 6-10 machines and some light for bld etc. Thanks in advance
Yes.
Have accessories (lites) on one circuit, track power on another and switch machine power on another. Less chance for something to interfere with another.
Absolutely.Even more,it is a good idea to assign wire color/gauge combination to specific tasks so that when you have some troubleshooting to do(I bet you will some day),it is much easier to find your way around.Better still is having quick disconnect plugs so that circuits can be separated easily ,which helps isolating a faulty circuit.
And the ultimate precaution is to draw a clear diagram of the layout circuit to keep available for further use.One may have a clear idea of his wiring spaghetti when he just finished it but what about in say four years later?
I can see the ground being on a bus, but the “firing” wires (for L and R) surely need to be separate for each individual machine, don’t they?
A separate power supply for t he turnouts is a great idea. If you are short on power supplies for this, then build or buy a capacitor discarge unit to run off what ever power supply is available. The CDU will make a very firm action for your turnouts, and charge itself up again from any source you give it.