A simple 18 or more contact rotary switch will work. You will not need to operate more than one stall at a time. More than 18 if you have external stalls adjacent to the 18 stall round house. Hook up the rotary switch in series with the turn table track and in series with a momentary push button switch used when you want to move engines (push button switch shown black below).
Turntable construction is detailed in post on page one of the below topic.
https://ogrforum.ogaugerr.com/...ra-027-layout?page=1
Charlie
